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  • 1980-1984  (4,415)
  • 1965-1969  (2,130)
  • Physics  (4,506)
  • Computational Chemistry and Molecular Modeling  (1,913)
  • Insulin
  • Nuclear reactions
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  • 1
    ISSN: 1432-1440
    Keywords: Aldosterone ; Glucose ; Insulin ; Potassium ; Renin-angiotensin system ; Cortisol ; Captopril
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Glucose loading is known to cause acute suppression of plasma aldosterone and stimulation of plasma renin activity. The relative contribution of variations in circulating angiotensin II to the regulation of aldosterone secretion following glucose loading was assessed in ten normal subjects. The effects of a standard oral glucose loading test (100 g) on plasma concentrations of glucose, insulin, potassium, aldosterone, renin activity and cortisol were studied (a) under basal conditions, and (b) after inhibition of angiotensin II with the converting enzyme inhibitor captopril (50 mg t.i.d. during 3 days). Under basal conditions the acute increase in plasma glucose and insulin after glucose loading was accompanied by a significant decrease (P〈0.01) in plasma cortisol and aldosterone and by a significant increase in plasma renin activity (P〈0.01); plasma potassium was decreased slightly but not significantly. Following captopril treatment preloading plasma renin activity was increased significantly, most probably reflecting an effective reduction of angiotensin II. Glucose loading caused a similar suppression of plasma aldosterone, as observed under basal conditions. This observation suggests that renin activation does not substantially contribute to the acute regulation of plasma aldosterone after an oral glucose load.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 62 (1984), S. 523-530 
    ISSN: 1432-1440
    Keywords: Neurotensin ; Gastrointestinal hormones ; Gastric secretion ; Pancreatic secretion ; Motility ; Insulin ; Glucagon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurotensin is a tridecapeptide originally isolated and characterized from bovine hypothalamus and later, in identical form, from bovine and human intestine. In the rat about 85% of immunoreactive neurotensin is found in the gut and about 10% in the brain. When an antibody specific for the amino terminal region of neurotensin was used the highest concentrations were found in the mucosa of the ileum, while an antibody specific for the biologically active region, the carboxyl terminus, also detected large amounts in the mucosa of the upper gastrointestinal tract. After a meal neurotensin — as measured by carboxyl terminal antibodies — rises after 5 min, a time in which the chymus has not yet reached the ileum, the main source of whole neurotensin. It is therefore possible that the carboxyl terminal molecules of neurotensin, found in the upper gastrointestinal tract, play an important physiological role. In plasma, neurotensin is rapidly degraded into smaller amino terminal and therefore biologically inactive molecules. Increases of carboxyl terminal neurotensin have been found in plasma in only a very few studies. The nature of this immunoreactive material has not yet been established. Therefore, the physiological role of neurotensin as a circulating hormone is unknown. Potential actions of neurotensin include thermoregulation, regulation of hormone release from brain (pituitary hormones) and gut (glucagon, insulin, somatostatin, pancreatic polypeptide), increase of vascular permeability, vasodilatation, inhibition of gastric acid secretion, stimulation of pancreatic secretion and changes of gut motility from the fasting to the fed type.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-8580
    Keywords: Oscillations ; Insulin ; Glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was designed to determine the effect of low dose continuous and oscillatory intraportal insulin infusions upon subsequent glucose-induced insulin release. In overnight-fasted and anesthetized rats with indwelling catheters in the jugular vein, carotic artery, and mesenteric vein insulin was infused intraportally for 3 h via the mesenteric vein catheter at a continuous rate of 45 µU/kg·min, or the same amount of insulin was administered at alternating high (72 µU/kg·min) and low infusion rates (18 µU/kg·min), respectively, in 2-, 4-, 8-, and 16-min cycles (oscillatory infusions). Another group received a continuous infusion of saline. Glucose (0.4 g/kg) was given i.v. 30 min after the end of the insulin or saline infusion. During the 3-h infusion of insulin or saline the peripheral glucose level remained unchanged in all groups. In response to the i.v. glucose load peripheral arterial plasma insulin levels were significantly elevated after preceding oscillatory infusions compared to the continuous insulin infusion. As compared to the group receiving saline the glucose-induced insulin response after continuous insulin infusion was significantly reduced. The plasma glucose responses were not different except for inexplicably elevated glucose levels in the 4-min cycle group. No difference was observed for plasma glucagon levels in all groups. The present data demonstrate an augmented responsiveness of theβ-cell to glucose after a preceding oscillatory infusion of insulin and an impaired responsiveness to glucose after continuous insulin infusion. This indicates that an oscillatory insulin release might be of importance for an adequate regulation ofβ-cell function.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 27 (1984), S. 373-378 
    ISSN: 1432-0428
    Keywords: Insulin ; administration and dosage ; therapeutic use ; insulin infusion devices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The tendency of insulin to form insoluble aggregates is a major obstacle to the development of implantable insulin infusion systems for treatment of insulin-deficient diabetic patients. A test system was developed to examine the kinetics of insulin aggregation under controlled conditions of temperature, vibration and contact material in an effort to provide design criteria for minimising aggregation. The contact materials tested were all potentially suitable for pump reservoirs on engineering criteria and included metals (stainless steel, titanium and a titanium alloy) and various plastics (polypropylene, polytetrafluoroethylene, Polyvinylchloride, polyamide, cellulose butyrate and silicone elastomer). The rate of insulin aggregation was markedly affected by the nature of the contact material. Hydrophilic materials, particularly polyamide and cellulose butyrate (2% of total insulin aggregated after 96 h vibration), appeared more compatible with insulin stability than did hydrophobic ones, such as polypropylene (16% aggregation) and Polyvinylchloride (37% aggregation). A specially formulated ‘pump’ insulin preparation, stabilised by addition of polyethylenepolypropyleneglycol, was significantly superior (three to five times more stable) to a regular neutral insulin formulation under most, but not all, conditions. Standard clinical syringes (polypropylene) performed poorly with both insulin formulations but especially with the neutral regular insulin (100% aggregation after 96 h vibration). In addition to physical aggregates, significant amounts (5%–30%) of the insulin remaining in solution were no longer detectable by immuno- or receptorassay in all materials tested. Appropriate combinations of insulin formulations and materials can minimise insulin aggregation and denaturation, but since the mechanisms involved are as yet poorly understood, realistic testing of proposed reservoir components and insulin formulations must be a prerequisite in insulin infusion pump planning and design. These testing procedures should be designed to test for denaturation in solution as well as for precipitation of insulin.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0428
    Keywords: Insulin ; insulin antibody ; immunogenicity ; immune response genes ; haemocyanin ; HLA ; DR7 ; C2 ; C4 ; factor B ; Gm ; C-peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Seventy-nine patients were observed prospectively during their initial period of treatment with conventional bovine insulins. Insulin antibody levels 6 months after starting insulin therapy did not correlate with age, gender or β cell function at onset of treatment. Patients who required soluble insulin in addition to isophane insulin developed higher levels of insulin antibody. Patients bearing the HLA-B8, DR3 and C4AQO alleles had lower levels of insulin antibody, whereas those bearing DR7 produced significantly higher levels. Other alleles at the C4A, C4B, C2, factor B or Gm loci did not appear to have a significant effect on insulin antibody production. The hyporesponsiveness of B8/DR3/C4AQO-positive individuals probably reflects a non-specific abnormality of immunity whereas the enhanced responsiveness of those positive for DR7 suggests the presence of a specific immune response gene for insulin
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0428
    Keywords: Insulin ; gastric inhibitory polypeptide ; insulin sensitivity ; glucose tolerance ; diabetes ; diet ; fat ; rate of carbohydrate digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study examined the acute effects of coingestion of fat (37.5 g) on the post-prandial metabolic responses to 75 g of carbohydrate which was either slowly absorbed (lentils) or rapidly absorbed (potatoes). Co-ingestion of fat resulted in a significant flattening of the post-prandial glucose curves, the effect being more pronounced for the rapidly absorbed potatoes. This was probably due to delayed gastric emptying. However, the post-prandial insulin responses to either carbohydrate were not significantly reduced by fat, suggesting that the insulin response to a given glucose concentration was potentiated in the presence of fat. The gastric inhibitory polypeptide (GIP) responses to both carbohydrates were greatly increased in the presence of fat. To investigate further the possible roles of GIP in the entero-insular axis, a 5-g bolus of glucose was injected intravenously 1 h after lentils ± fat. This was sufficient to raise the glucose levels above the threshold reported for GIP to potentiate insulin secretion. However, despite the large differences in circulating GIP levels, the insulin response to glucose was not affected by the presence of fat. These results suggest that (1) the rate of absorption of carbohydrate is a major determinant of post-prandial metabolic responses even in the presence of fat, (2) fat-stimulated GIP secretion does not potentiate glucose-induced insulin secretion, and (3) the potentiation of the insulin response to glucose when carbohydrate is co-ingested with fat is consistent with the well-documented insulin resistance associated with high fat diets.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0428
    Keywords: Insulin ; 3-hydroxy-3-methylglutaryl coenzyme A ; sterol synthesis ; human mononuclear leucocytes ; post-transcriptional regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Incubation of freshly isolated human mononuclear leucocytes in lipid-depleted serum for 4 h resulted in a two-fold increase in 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. Insulin, when added to the incubation medium at concentrations of 10 and 100 nmol/l at zero time, caused additional increases in the enzyme activity of 30% and 37%, respectively. The hormone action was not immediate because no effect was observed when insulin was added at 4 h and activity examined thereafter. Under these conditions sterol synthesis from 14C-acetate and tritiated water was strictly proportional to the activity of HMG-CoA reductase. Cycloheximide (20 μg/ml), a translational inhibitor of protein synthesis, prevented the insulin-mediated increase in the enzyme activity and the incorporation of 14C-acetate into sterols. Cordycepin (50 μg/ml) inhibited messenger RNA synthesis by 〉 50%, but had no inhibitory effect on the induction of HMG-CoA reductase and sterol synthesis. Low density lipoprotein (80 μg protein/ml) and complete serum blocked the induction of the enzyme and sterol synthesis from 14C-acetate caused by lipid-depleted serum. The insulin-effect, however, remained unchanged. The results suggest that insulin may regulate the de novo synthesis of HMG-CoA reductase and accordingly sterol synthesis at a post-transcriptional level.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Intensive care medicine 10 (1984), S. 209-211 
    ISSN: 1432-1238
    Keywords: Amitriptyline ; Hydrocortisone ; Insulin ; Prenalterol ; Cardiac failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case of severe amitriptyline poisoning with grade IV coma, seizures, bradycardia and hypotension who did not respond to dopamine was successfully treated with prenalterol, a new cardioselective β-agonist. The case is discussed with respect to plasma concentrations of dopamine, prenalterol and amitriptyline. Prenalterol, hydrocortisone and insulin may be useful as inotropic agents in tricyclic poisoning where dopamine fails to provide an adequate response.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 400 (1984), S. 413-417 
    ISSN: 1432-2013
    Keywords: Sodium pump ; Na-K ATPase ; Na fluxes ; Vanadate ; Insulin ; Skeletal muscle ; Ouabain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have measured the effects of concentrations of vanadate ranging between 0.01 and 10 mM on the22Na efflux of frog sartorius muscles. The addition of vanadate had no effects when concentrations lower than 0.5 mM were used; higher concentrations increased Na efflux. The increase was abolished by the addition of ouabain (10−5M). In muscles pretreated with ouabain vanadate did not modify Na efflux. The stimulatory effects of vanadate on Na efflux were also observed in Na-free solutions indicating that the effux of vanadate was not caused mainly either by an increase in the exchange of Na for Na or by an increase in Na entry into the muscle. We also examined the effects of vanadate on muscles immersed in solutions containing 20 mM K+; both vanadate and increased K+ produced stimulations of Na efflux that were additive. Similarly when the effects of vanadate and insulin were measured on the Na efflux of the same muscle, additive effects were found. As the ouabain-sensitive Na efflux in frog muscle is generally agreed to be due to the activity of the Na-K ATPase, our findings suggest that the net effect of vanadate in intact muscle cells is an increase in the activity of the Na pump. Since vanadate affects many enzymes it is quite possible that the stimulatory action is not due to a direct effect on the Na-K ATPase but may be mediated through an intermediary step. Regardless of the specific mechanism, it is evident that, our results as well as other findings in the literature, strongly indicate that Na pumping by intact cells can be increased by vanadate administration. Hence it is not justified to attribute the physiological modifications caused by vanadate administration to blockade of the Na-K ATPase unless the attribution is justified by specific experimental evidence.
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  • 10
    ISSN: 1432-2013
    Keywords: Biological transport ; Insulin ; Energy metabolism ; Epinephrine ; Endocrinology ; Albuterol (salbutamol) ; Active sodium-potassium transport ; Muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The total metabolic energy expenditure associated with active Na−K-transport over the first 20 min of stimulation with insulin, adrenaline or salbutamol (ΔHmNa−K) was determined from direct calorimetric and tracer ion flux measurements in isolated muscles at rest. The reversible work performed by the Na−K-pump during the same interval of time (WrevNa−K) was calculated as the product of the ouabain-suppressible Na−K transfers and the mean free energy increase imparted to the two ions as they are transported against their electrochemical gradients across the plasma membrane. Comparison of membrane potential and intracellular Na and K concentrations before and after the stimulations indicated that part of WrevNa−K had contributed to increase the ion electrochemical gradients in the preparation (i.e. had not been lost as heat) during the 20 min period. Accordingly, the maximum value of ΔHmNa−K was taken as the sum of the ouabain-suppressible heat production and WrevNa−K. Following stimulation with insulin, adrenaline or salbutamol this maximum corresponded to 10, 10 and 12% respectively, of basal metabolism. Under the same three conditions, the minimum “energetic efficiency” of the active Na−K-transport process, defined as the ratio between WrevNa−K and maximum ΔHmNa−K, was 35, 41 and 38%, respectively.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 142 (1984), S. 179-185 
    ISSN: 1432-1076
    Keywords: Craniopharyngioma ; Growth ; Insulin ; Neurosurgery ; Radiotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Management of craniopharyngiomas is still controversial. 28 children with this tumor were studied. GH deficiency was present in 22 patients following surgery, 10 of these GH-lacking patients had normal or accelerated growth (usually associated with rapid weight gain) postoperatively. Somatomedin levels were normal in three of six normally growing patients. After craniotomy their basal and TRH-stimulated prolactin levels were in the normal range, but their insulin secretion was markedly increased. Postoperatively there was a significant correlation between peak insulin levels following arginine infusion and growth velocity in all patients. Complete tumor removal could be performed in 28% of our patients. Altogether 36% of all patients had at least one tumor recurrence. Recent literature with the addition of our series showed tumor recurrence in 22% of patients with “total” tumor excision and in 72% of patients with partial tumor removal. Radiotherapy seems to be capable of destroying craniopharyngioma tissue. The recurrence rate was only 26% in patients with subtotal excision plus radiotherapy. Unless radical tumor removal can be attempted with safety, subtotal tumor removal plus radiotherapy appears to be the treatment of choice for craniopharyngioma.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 237 (1984), S. 169-179 
    ISSN: 1432-0878
    Keywords: Foetal pancreas ; β Cells ; Insulin ; Fasting mothers ; Morphometry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary After maternal fasting for 72 h the pancreatic β cells of 18-day-old foetal rats show a conspicuous enrichment in secretory material, with an increase of pancreatic insulin concentration and a marked development of the rough endoplasmic reticulum and the Golgi apparatus. The morphometric analysis shows that the intracytoplasmic migration of the secretory granules is inhibited, principally inside the cell web. Consequently the number of secretory granules fused with plasma membrane decreases and this is associated with a decreased foetal plasma insulin. The difference in the ultrastructural aspect of the β cells of foetuses from fasting mothers and of foetuses from fed mothers is less conspicuous at 19 days of gestation and progressively disappears at 20 and 21 days. The modifications in ultrastructural aspect and in functional state are discussed.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 53 (1984), S. 57-62 
    ISSN: 1439-6327
    Keywords: Muscle glycogen ; Time sequence ; Free fatty acids ; Insulin ; Exercise in humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To evaluate the metabolic and hormonal adaptations following a rapid change in muscle glycogen availability, 14 subjects had their muscle glycogen content increased in one leg (IG) and decreased in the other (DG). In group A (n=7), subjects exercised on a bicycle ergometer at 70% maximal oxygen uptake for 20 min using the DG leg. Without resting these same subjects exercised another 20 min using the IG leg. Subjects in group B (n=7) followed the same single-leg exercise protocol but in the reverse order. In order to get some information on the time sequence of these possible adaptations, blood samples were collected at rest and at the beginning and the end of each exercise period (min 5, 20, 25, and 40). Results indicated that 5 min after the switch from the DG leg to the IG leg. transient increases in plasma free fatty acids (1.20 to 1.39 meq·l−1) and serum insulin (10.1 to 12 mU·l−1) concentrations occured. Between minute 25 and 40 of exercise, the DG to IG switch was accompanied by a decrease in free fatty acids and glycerol concentrations as well as an increase in lactate levels. An opposite response was observed in the IG to DG condition during the same time span. Plasma norepinephrine, epinephrine, glucagon, and serum cortisol concentrations were not significantly affected by the leg change. These results suggest a rapid preferential use of muscle glycogen when available and a time lag in the response of the extramuscular substrate mobilization factors.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 53 (1984), S. 267-273 
    ISSN: 1439-6327
    Keywords: Exercise ; Triglycerides ; Free fatty acids ; Glycerol ; Insulin ; Catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Metabolic and hormonal responses to prolonged treadmill exercise in dogs fed a fat-enriched meal 4 h prior to the exercise were compared to those measured 4 h after a mixed meal or in the postabsorptive state. Ingestion of the fat-enriched meal caused significant elevations in the resting values of plasma triglyceride (TG), free fatty acid (FFA), and glycerol concentrations. A reduction of the plasma TG concentration (from 1.6±0.2 to 1.1±0.10 mmol·l−1,P〈0.005) occurred only in dogs exercising after the fat-enriched meal. No significant changes in this variable were noted in dogs fed a mixed meal, whilst in the postabsorptive state exercise caused an increase in the plasma TG level (from 0.42±0.03 to 0.99±0.11 mmol·l−1,P〈0.01). The exercise-induced elevations in plasma FFA and glycerol concentrations were the highest in the dogs given the fat-enriched meal. Plasma glycerol during exercise correlated with the initial values of circulating TG (r=0.73). The plasma FFA-glycerol ratio, at the end of exercise was lowest in the dogs taking the fat-enriched meal (1.39±0.19), suggesting an increased utilization of FFA in comparison with that in the postabsorptive state (3.27±0.37) or after a mixed meal (2.88±0.55). Basal serum insulin (IRI) concentrations were similarly enhanced in dogs fed fat-enriched and mixed meals, and they were reduced to control values within 60 min of exercise. Plasma adrenaline and noradrenaline concentrations correlated with time of exercise (r=0.84 andr=0.96, respectively) and were unaffected by the nutritional modifications. It is concluded that ingestion of a single fat-enriched meal considerably modifies the exercise-induced changes in lipid metabolism. The pattern of changes in plasma TG, FFA, and glycerol concentrations indicates an enhanced hydrolysis of plasma chylomicron-TG, suggesting that this lipid source may contribute markedly to exercise metabolism.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 52 (1984), S. 426-430 
    ISSN: 1439-6327
    Keywords: Apoproteins ; Lipoproteins ; Insulin ; Blood lactate ; Physical training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eight well-trained males were studied before, during and after 6 months of a progressively increased amount of endurance training in order to elucidate the effects on the apoproteins and apo-lipoproteins. Initially high HDL-cholesterol levels were revealed (1.62±0.15 mmol×l−1, mean ± SE.). After a transient but not significant, slight decline at the onset of the increased training program (1.57±0.06 mmol×l−1) HDL-cholesterol increased gradually to the end of the training period (1.92±0.12 mmol×l−1). There was an increased aerobic capacity as judged by maximal oxygen uptake and by lactate concentration during standardized submaximal work. However, at the end of the training period, a levelling off in maximal oxygen uptake was revealed, while HDL-cholesterol was still increasing. The present data demonstrate that HDL can be influenced by training at all levels of aerobic capacity.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 201-209 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic spectra of PdCl42- and PtCl42- are studied by quantum-chemical methods with the ultimate object being to understand the differences in reactivity for Pt(II) and Pd(II) complexes. Nonrelativistic ab initio UHF, DV - Xα, and MSXα methods give very similar assignments of the spectra for PdCl42-. The d-d spectrum for PtCl42-, which is very different from the d-d spectrum of PdCl42-, agrees qualitatively with the spectra obtained using the relativistic extended-Hückel (REX) and Dirac-Slater (DS) methods. Although the latter two methods disagree somewhat in the interpretation of the high intensity bands in PtCl42-, it appears reasonable to interpret at least one of the lines as a 5d → 6p transition.
    Additional Material: 5 Ill.
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  • 17
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relativistically parameterized extended-Hückel (REX) calculations concerning species and exchange reactions in the system I or I* + I2 are reported, where I = 2P3/2 and I* = 2P1/2. From their experimental data for related halogen systems X + YZ XY + Z, E. B. Gordon, A. I. Nadkhin, S. A. Sotnichenko, and I. A. Boriev [(Chem. Phys. Lett. 86, 209 (1982)] have proposed a conservation rule for the spin-orbit state (X* → Z*, X → Z). The results of REX calculations, double-group symmetry analysis, and schematic state correlation diagrams reported here are consistent with the proposed conservation rule. Two of the transition states are linear and the third nearly so, but no Γ1/2-Γ3/2 crossings leading to spin-orbit conversion are found.
    Additional Material: 4 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 47-55 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of the relativistic investigation of the energy spectra and the electronic transitions in the case of complex configurations, based on the theory of the irreducible tensorial operators and the genealogical coefficients, is described. The use of the quasispin and isospin technique in the relativistic approximation is discussed. Expressions are presented for electric multipole transition probabilities for general values of the gauge condition of electromagnetic field potential.
    Additional Material: 2 Tab.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 23-46 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent developments in relativistic atomic structure have been more in terms of program improvement than in fundamental theory. Some comments on both aspects of this work are illustrated by a description of two different recent applications. In the first, we study the contribution of the interaction of relativity and correlation to the 2 3S-2 3P0,1,2 intervals in heliumlike ions, whose theoretical estimation is important for testing QED. The study of satellite structure in the Kβ x-ray emission spectrum of Ar illustrates a quite different use of the program packages developed at Oxford for investigating configuration interaction. The use of shake theory to predict the initial states, populated along with the primary vacancy giving rise to the diagram line, gives a satellite line intensity distribution which agrees very well with recent experimental spectra.
    Additional Material: 4 Ill.
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  • 20
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isospin basis is put into operation for investigation of atomic configurations, having two shells of equivalent electrons, characterized by the same orbital (LS coupling) or total (jj coupling) angular momenta of each electron. Tensorial properties of both the operators and the wave functions are studied in this basis. The two-particle operator is expressed in terms of the tensors irreducible in the isospin space. The problem of the additional classification of the levels is considered. The accuracy of the quantum numbers of the isospin basis in jj coupling scheme is discussed.
    Additional Material: 2 Tab.
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 79-96 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The S-matrix formalism is used to treat the phenomenon of resonance energy transfer (sensitized fluorescence). It is shown that for dipole-allowed transitions and short sensitizer-acceptor separations, the relativistic treatment yields the same result as the nonrelativistic Perrin-Förster theory. For large sensitizer-acceptor separations, long-range coupling terms appear in the relativistic treatment. Resonance energy transfer through these long-range coupling terms is compared with spontaneous photon emission, and direct-interaction theories of electromagnetism are discussed. In the Appendix it is shown that the relativistic theory predicts resonance transfer of triplet excitation energy through the spin-spin coupling term in the Breit interaction.
    Additional Material: 3 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 131-148 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods of calculation of potential energy curves or surfaces, including dissociation energies, bond distances, and vibration frequencies, are discussed as well as recently obtained results for several molecules. The ab initio relativistic methods involve the derivation of “shape-consistent” effective potentials from Dirac-Fock atomic calculations. These effective potentials are averaged and differenced with respect to spin with the differences, p3/2 - p1/2, etc., yielding spin-orbit operators. The molecular calculations are then set up in a familiar manner through the SCF stage using spin-averaged effective potentials. The final stage is a configuration-interaction calculation including the spin-orbit terms as well as the electron repulsion terms. Calculations that have been made for several low-lying excited states as well as the ground state for Au2, TlH, Tl2, Sn2, and Pb2 are reviewed. Good agreement is obtained with spectroscopic data and a number of interesting predictions are made.
    Additional Material: 8 Ill.
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  • 23
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 263-263 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 24
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 273-273 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 25
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 309-320 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The group structure of simple graphs can be found by factoring the adjacency matrix into cyclic blocks. The blocks correspond to permutational subgroups of the graph. The overall group structure is a product of the independent subgroups.
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  • 26
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    International Journal of Quantum Chemistry 25 (1984), S. 355-365 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two techniques are presented for reducing the effort required to determine localized orbitals based on the energy or density criteria. The first, population weighted editing of the electronic repulsion integrals, reduces the effort required for each iteration of the localization procedure. The second, damping/extrapolation of the transformation matrix, reduces the number of iterations required to reach convergence. Numerical results are provided for methane and formaldehyde (for the editing method) and for carbon monoxide and boron fluoride (for the damping/extrapolation technique).
    Additional Material: 4 Tab.
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  • 27
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 28
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 475-481 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In describing mesomer structures by the original PCILO method several problems may occur because of the use of localized bonds. A so-called VB-PCILO including a superposition of several mesomer boundary structures in the CI perturbation treatment will be proposed.
    Additional Material: 1 Ill.
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  • 29
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    International Journal of Quantum Chemistry 25 (1984), S. 677-686 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibration-rotation levels for the diatomic RKR potential curve are solved using both perturbational and variational approaches. To obtain any-order correction of the energy from unperturbed parameters, an iterative scheme is formulated in the hypervirial framework. Variational calculations are carried out upon a rotationless Morse oscillator basis set and using a transformation technique to treat the effective potential energy function. Numerical results for the RbH X 1Σ+ state are obtained. The accuracy of the energy levels is tested by solving the Schrödinger equation by a numerical procedure.
    Additional Material: 5 Tab.
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  • 30
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    International Journal of Quantum Chemistry 25 (1984), S. 723-731 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the factors that contribute to the stability of the bond between alkali metal atoms is made by using nonorthogonal configuration interaction. Beyond the orbital size, the overlap of the valence orbitals of one atom with the core orbitals of the other accounts for most of the difference between the hydrogen molecule and the alkali metal diatomics. It is shown that the valence bond description does not provide a satisfactory description in any case except for the hydrogen molecule, and valence electron correlation using the p-type valence orbitals is essential.
    Additional Material: 3 Tab.
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  • 31
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    International Journal of Quantum Chemistry 25 (1984) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 32
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of vibronic coupling between two harmonic CBO potentials with equal minima positions on the electronic absorption and emission spectra is investigated in the framework of our model using the variational procedure. The numerical results, being identical with those obtained through the vibronic coupling model of Fulton, Gouterman, and Brickmann, are discussed with regard to the longest-wavelength electronically forbidden transition, its vibrational structure, and the Stokes loss.
    Additional Material: 5 Ill.
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  • 33
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    International Journal of Quantum Chemistry 25 (1984), S. 743-752 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational properties of 3-deazapurine nucleosides (namely, 3-deazaadenosine and 3-deazaguanosine) have been investigated by the PCILO method. Both C(2′)-endo and C(3′)-endo sugar puckers have been considered and the results indicate that the conformational preferences of these nucleoside analogs are quite different from those of their parent nucleosides adenosine and guanosine, respectively. This result has been correlated in terms of the biological inactivity of these nucleoside analogs.
    Additional Material: 4 Ill.
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  • 34
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A recently proposed orbital optimization technique based on the use of the inverse of the level-shifted Fock operator is successfully applied to a large number of pathologically divergent cases. The possibility of eliminating convergence problems by adopting a similar modification in the operation of the orthogonal gradient method is also successfully tested.
    Additional Material: 1 Ill.
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  • 35
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    International Journal of Quantum Chemistry 25 (1984), S. 817-851 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The band structure of porphyrinatonickel(II) (2) has been studied by means of crystal orbital calculations that are based on the tight-binding approximation; the computational framework is a recently developed INDO model for transition metal compounds of the 3d series. The porphyrinato polymer has been studied in an eclipsed arrangement (2a) and in a staggered conformation (2b) where neighboring layers are rotated by 41°. The total energy of the metallomacrocycle has been decomposed into one- and two-center contributions; the latter interaction parameters have been fragmented into physically feasible resonance, exchange, and classical electrostatic (electron-electron, electron-core, core-core) interactions. It is shown that individual two-center potentials between atoms in neighboring layers are prevailingly determined by the electrostatic interaction energy. The NiNi coupling in the chain is highly repulsive; important stabilizing interactions are predicted between the 3d center of one cell and the electronegative N atoms in the neighboring layers. Stabilizing and destabilizing electrostatic interaction potentials largely compensate each other; the net stabilization in the polymer comes from the accumulation of resonance and exchange increments. The unoxidized Ni(II) porphyrinato polymer is an insulator. Several ligand bands (π, σ, and lone-pair) are predicted on top of bands with significant Ni 3d admixtures; the conduction band of the unoxidized strand is of ligand π* character. The dense manifold of ligand states in the vicinity of the Ni 3d states (3dz2, 3dx2-y2, 3dxz/3dyz) prevents the formation of bands in the polymer that are strongly localized at the 3d center. Ni 3dz2 and 3dx2-y2 interact strongly with ligand lone-pair and σ states. Avoided crossings between ∊(k) curves in k space lead to compositions in the various bands that differ significantly at the bottom and the top. The INDO crystal orbital formalism predicts a partial oxidation of ligand bands in derivatives of 2 that contain oxidants (e.g., halides). The theoretical findings derived for 2 are compared with available experimental data on highly conducting porphyrinatonicke(II) polymers (tetrabenzo and octamethyltetrabenzo derivatives of 2).
    Additional Material: 15 Ill.
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  • 36
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    International Journal of Quantum Chemistry 25 (1984) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 37
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    International Journal of Quantum Chemistry 25 (1984), S. 1023-1033 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variational functional method is improved and generalized in order to obtain approximate bound-state energies of a wide variety of quantum-mechanical systems. Calculations on the discrete spectrum of the hydrogen atom in a magnetic field and the bounded harmonic oscillator show that the procedure is very promising.
    Additional Material: 2 Ill.
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  • 38
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    International Journal of Quantum Chemistry 25 (1984), S. 1055-1060 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CNDO/BW modification of the CNDO/2 approximation was used within the PCILO framework. It was shown on some significant examples that all the good results of the original PCILO-CNDO/2 method can be reproduced by the modified version PCILO-CNDO/BW at least. Thus, preserving the quality of its results a computer-expense-reduced PCILO method is proposed for calculations on large molecular systems.
    Additional Material: 1 Ill.
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  • 39
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    International Journal of Quantum Chemistry 26 (1984), S. 197-212 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio Hartree-Fock method devoted to the study of polymers is presented, truncation criteria for the exchange and the Coulomb series are discussed, and it is shown that the error in the total energy evaluation can be reduced to below 0.0001 a.u./cell with little computational effort. Results for six polyacetylene isomers are presented and compared with previous ab initio data obtained using the same basis set. In agreement with the experimental findings, the alternating all-trans structure is the most stable.
    Additional Material: 2 Ill.
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  • 40
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    International Journal of Quantum Chemistry 26 (1984), S. 237-250 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new minimum basis set was developed for use in computing excitation energies of large molecules. It is particularly suited to calculating ionization potentials and Rydberg transitions. Pyrrole excitation energies and oscillator strengths calculated with this basis set are compared to larger basis set ab initio and semiempirical results. The 6-eV band in the experimental spectrum is predicted to be the result of three Rydberg absorptions, with no underlying (π, π*) absorption. The calculations also provide an explanation for the observed N—H stretch in the 6-eV region.
    Additional Material: 2 Ill.
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  • 41
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    International Journal of Quantum Chemistry 26 (1984), S. 251-274 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio methods have been used to calculate the ground and excited states of “normal” and “hyper” porphyrins. Perturbation theory and CI methods were used to determine differential ground and excited-state correlation effects for [Pv(P)F2]+ and [PIII(P)]+. A comparison is made to the INDO/S/CI predicted wavefunctions and spectra and to the experimental spectra of closely related molecules. The “hyper” [PIII(P)]+ calculations show some very low energy electronic transitions which provide an explanation for an anomalous “red” band in the spectrum and for the lack of fluorescence. Ab initio calculations also predict that (1) the lowest energy 1A1 state is a two-configuration wavefunction which can be described as a diradical, (2) the two lowest-energy singlet excited states are double excitations from the closed shell SCF configuration, and (3) a 3B2 state is very close in energy to the lowest 1A1 state.
    Additional Material: 9 Ill.
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  • 42
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    International Journal of Quantum Chemistry 26 (1984), S. 339-347 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The operator technique with a minimum of commutator algebra is employed to calculate matrix elements of any number of operators between distorted, displaced harmonic oscillator wavefunctions. The results are valid for multidimensional integrals, and regardless of the extent of the Duschinsky effect. General recursion relations useful in machine calculations are given. The formalism is illustrated for the well-known one-dimensional Franck-Condon integrals.
    Additional Material: 1 Tab.
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  • 43
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    International Journal of Quantum Chemistry 26 (1984), S. 383-403 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The multiple bond description supplied by localized molecular orbitals obtained within the ZDO approximation is analyzed. In particular, conditions for the appearance of σ-π separation and of continuous degeneracy of the localization sum against σ-π mixing are given for two current ZDO energy- and density-localization methods. Likewise, a convenient modification of the latter is presented together with some illustrative examples.
    Additional Material: 2 Ill.
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  • 44
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    International Journal of Quantum Chemistry 26 (1984), S. 125-143 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper shows that the spin-shift formalism developed in B. T. Pickup and A. Mukhopadhyay [Int. J. Quantum Chem. 26, 101 (1984)] supports a one-component diagrammatics which has a systematics akin to that in the spin-orbital many-body theory. The diagrams are neither Goldstone nor Yutsis type, and characterize the chain U(2R) ⊃ U(R)⊗SU(2) on which the spin-shift formalism is based. Accordingly, while the lines in such diagrams are labeled by the orbital indices, the diagram structure adequately reflects the irreducible representation of the group U(R). In this sense the paper presents a unitary group approach to the natural generalization of the usual many-body theory for the spin-adapted cases. A set of very simple rules is derived; their similarity with the corresponding rules in the ordinary many-body theory and practical utility are discussed in connection with (a) matrix elements over many-electron spin states and (b) closed- and open-shell many-body perturbation theory. A possibility of integral-driven many-body perturbation theory for open-shells is indicated. Connections of this formalism with others are also discussed.
    Additional Material: 11 Ill.
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  • 45
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    International Journal of Quantum Chemistry 26 (1984), S. 183-196 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The equilibrium geometry of formhydroxamic acid has been calculated within the framework of the INDO-MO formalism. Various structural factors are analyzed and discussed in terms of the calculated force constants and charge distribution. The possibility of internal rotation around the C—N bond of formhydroxamic acid has been examined. The potential energy surface for the amide-imide tautomerism is explored by calculating the geometries and characterizing saddle points on that surface. The cyclic and open dimers of formhydroxamic acid are examined and the hydrogenbond energy and length are calculated.
    Additional Material: 5 Ill.
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  • 46
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    International Journal of Quantum Chemistry 26 (1984), S. 479-488 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: From the density operator, some constants of the motion are defined and established. We suggest calling them conjunctural constants of the motion. It is proved that no more than n - 1 of them can be linearly independent. Using su(m) (m 〈 n ) subalgebra associated with the Hamiltonian-operator, it is shown how conjunctural constants of the motion can be expressed in terms of the coherence vector components.
    Notes: A partir de I'opérateur-densité d'un système quantique à n états, sont définies et calcultes des constantes du mouvement pour lesquelles est proposée I'appellation nouvelle de conjoncturelles. On établit qu'il en existe au maximum n - 1 linéairement indépendantes. A I'aide des sous-algèbres su(m) (m 〈 n ), on montre comment il est possible d'introduire, suivant la forme de I'hamiltonien, des constantes du mouvement conjoncturelles reliées aux composantes du vecteur de cohérence.
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  • 47
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    International Journal of Quantum Chemistry 26 (1984) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 48
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    International Journal of Quantum Chemistry 26 (1984), S. 593-605 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this survey paper the different possible theoretical ways of treating the SN2 reaction are explained. It is shown that, in the future, experience and theory will very likely complement each other.
    Additional Material: 5 Ill.
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  • 49
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    International Journal of Quantum Chemistry 26 (1984), S. 709-715 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of the chemical bond is very old. Many interpretations have been proposed. Nevertheless, the problem is far from being solved. At the present time, the chemist has the choice between two models: the Lewis model (electron pairs) and the quantum model. In spite of a current opinion, both models are not logically equivalent. The localization of molecular orbitals is only a mathematical operation which does not involve any physic localization of the electrons. The loge theory is not more satisfying owing to the fact that loges with minimal fluctuation do not exist in all molecules. The theory of orbital domains seems to bring a solution. Nevertheless, its interpretation can be obtained only outside the strict framework of quantum mechanics.
    Additional Material: 1 Tab.
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  • 50
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    International Journal of Quantum Chemistry 26 (1984), S. 717-723 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some mathematical implications of the extended nature of model chains are reviewed to call attention to their importance in electronic structure calculations at the restricted Hartree-Fock Roothaan level.
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  • 51
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    International Journal of Quantum Chemistry 26 (1984), S. 753-768 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of an impurity in a quasi-one-dimensional system is addressed. A hydrogen atom in a lithium chain serves as physical model. Two complementary descriptions, the cluster model approach with focus on local interactions, and the self-consistent Green's function approach which takes into account the extended nature of the system will be presented at the Hartree-Fock level. The results of both approaches are discussed in a comparative analysis.
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  • 52
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    International Journal of Quantum Chemistry 26 (1984), S. 793-822 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: After mentioning differences in C—O and Si—O bonding and different structural types of silicates, the conclusion that interactions between external partners and surfaces of silica and zeolites are mostly dominated by van der Waals forces is discussed. Consequently, the theoretical treatment includes (i) selection of appropriate cluster models, (ii) application of nonempirical quantum chemical methods for obtaining interaction potentials, and (iii) statistical thermodynamic evaluation of adsorption characteristics. As examples vibrational frequencies of H2O and NH3 adsorbed on cationic sites, the interaction of conjugated hydrocarbons with Na+ sites, and the interaction of H2O with various sites on silica and zeolite surfaces are considered.
    Additional Material: 6 Ill.
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  • 53
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    International Journal of Quantum Chemistry 26 (1984), S. 831-841 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this review we briefly outline the model developed by Collins and co-workers [T. C. Collins, A. B. Kunz, and R. S. Weidman, Recent Advances in Quantum Theory of Polymers, J. M. Andre et al., Eds., Lecture Notes in Physics (Springer-Verlag, New York, 1979), Vol. 113, p. 240; T. C. Collins, M. Seel, J. J. Ladik, M. Chandrasekhar, and H. R. Chandrasekhar, Phys. Rev. B 27, 140 (1983)] for CdS and CuCl. The model should be applicable to organic semi-conductors. It is the outgrowth of the work of Little [W. A. Little, Phys. Rev. 134, 1416A (1964)], Devreese et al. [J. T. Devreese, A. B. Kunz, and T. C. Collins, Solid State Commun. 11, 673 (1972)] and a large amount of literature concerning He3 p-state [A. J. Leggett, Rev. Mod. Phys. 47, 331 (1975)]. This model is built around calculated band structures and the polarization of the valence band by conduction electrons at moderately high impurity concentrations. We extend the model to include both singlet and triplet paired spin states. The parallel paired states contribute a paramagnetic term to the susceptibility, and we discuss the conditions for this term to dominate over the diamagnetic term.
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  • 54
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    International Journal of Quantum Chemistry 26 (1984), S. 857-872 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is suggested that the extreme efficiency and specificity observed for chemical reactions in biological systems (compared to chemical reactions occurring under common chemical conditions) is mainly due to special features of these reactions. A key position is ascribed to the role of weak intermolecular interactions (also called noncovalent or van der Waals); in addition, the important role of the entropy and of cyclic or cavitylike shapes of numerous reaction sites, together with the influence of strong local electric fields on transport phenomena and reactivity are discussed. The greatest attention is paid to the applicability of computational methods for evaluation of weak intermolecular interactions, ranging from beyond Hartree - Fock methods to empirical potentials.
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  • 55
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    International Journal of Quantum Chemistry 26 (1984), S. 917-931 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The arrangement of membrane-bound pigments, proteins, and lipids in the thylakoids of higher plants is described, and the role of the membrane in preventing the back-reaction is discussed. The photosynthetic bacterium halobacterium halobium is also described. A simplified quantum-mechanical picture of the primary process in photosynthesis is presented, and the mechanism of electron-hole separation in this picture is compared with the corresponding mechanism in a silicon solar cell. An appendix discusses the application of Frenkel exciton theory to the antenna effect.
    Additional Material: 12 Ill.
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  • 56
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    International Journal of Quantum Chemistry 26 (1984), S. 955-964 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A brief review is given of the three main known biochemical mechanisms of human oncogene activation. The underlying possible physical and chemical mechanisms (both short- and long-range) caused by chemical carcinogens are also briefly discussed. The probable role in carcinogenesis of conformational solitons generated after the release of carcinogens previously bound to nucleotide bases is pointed out. For such a soliton the Hamiltonian is written down and the solution of classical equations of motion is outlined.
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  • 57
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    International Journal of Quantum Chemistry 26 (1984), S. 943-953 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enzymes are catalysts occurring in living cells. The aim of this paper is to describe some basic properties of enzymes and to understand on a physical basis how the intracellular milieu may control the kinetics of enzyme reactions. We shall therefore consider in succession some kinetic properties of enzymes in solution and the way cell surfaces and biological membranes control the dynamics of enzyme reactions. The choice of topics which have been selected in this paper is somewhat arbitrary and certainly reflects the tastes and the personal interests of the authors.
    Additional Material: 8 Ill.
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  • 58
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that in the framework of the π-electron approximation even polyenes can be unambiguously divided into 4L- and 4L +2- classes. The classification scheme is based upon the sign alternation of the bond-order between the first and the last atoms and upon the different information content of the bond-order distribution for 4L- and 4L +2- polyenes, respectively. The classification has been shown to hold for the four lowest-lying electronic states: the ground state 1Ag-, the spectroscopically permitted excited state 1Bu+, the spectroscopically forbidden state 1Ag-, and the lowest triplet state 3Bu+ at all levels of sophistication in the π-electron approximation, ranging from the simple Hückel Hamiltonian to the PPP-multi-CI approach. It is shown that the proposed classification is valid also for heteropolyenes and polyenelike/heteropolyenelike fragments from complex organic molecules. The classification has been shown to be useful for the theoretical interpretation of thermo- and photoelectrocyclic reactions. The sign of the bond order between the first and the last atoms (or the average information content) determines unambiguously the topology of the forming cyclic transition state and, thence, the course and the mechanism of these reactions. The results obtained indirectly support the hypothesis that the lowest excited states in butadiene and hexatriene are of the type 1Bu+.
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  • 59
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    International Journal of Quantum Chemistry 26 (1984), S. vii 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 60
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    International Journal of Quantum Chemistry 26 (1984), S. 1039-1049 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hartree-Fock equations are viewed as nonlinear algebraic equations that can be solved iteratively. Provided we assume the existence of a solution, valuable properties of convergence may be assessed. The close connection between convergence of the SCF procedure and stability properties of the solution is shown from a nonapproximate standpoint. The convergence features of level-shifting convergence-forcing techniques are analyzed. The connection between this nonlinear algebraic approach and the related gap equation is displayed and the example of the restricted Hartree-Fock hydrogen molecule is discussed.
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  • 61
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    International Journal of Quantum Chemistry 26 (1984), S. 1017-1027 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents the first results of the application of quantum mechanics with complex coordinates to the calculation of partial widths for the radiationless decay of an inner-hole excited autoionizing state, the Ne+1s2s22p6 2S. This is succeeded by the reduction of the multi-electron, multichannel problem in the complex energy plane to five, symmetry adapted, two-electron problems, in accordance with a published theory of many-electron resonances. These two-electron problems are solved independently by using rotated analytic Hartree-Fock orbitals (expressed in terms of Slater orbitals) for the localized components, and Slater plus Gamow orbitals for the rotated, asymptotic square-integrable functions carrying the width information. A recently proposed variational principle is employed for the optimization of nonlinear parameters. Within this independent asymptotic pair approximation (IAPA), our results for the partial widths to the five Ne2+ channels are (in 10-2 a.u.): 1s-2p2 1D: 0.560, 1S: 0.048; 1s-2s2p, 3P0: 0.029, 1P0: 0.154; 1s-2s2, 1S: 0.044. The total width is 0.835. These numbers agree reasonably well with those obtained by Kelly [Phys. Rev. A 11, 556 (1975)] from a many-body perturbation theory (MBPT) calculation, and by Howat et al. [J. Phys. B 11, 1575 (1978)] from a configuration-interaction in the continuum calculation. The most recent experimental results yield 0.604, 0.089, 0.063, 0.174, and 0.060, respectively, with a total width of 0.99. Previous real-coordinate many-electron calculations by Beck and Nicolaides-including relativistic and radiative effects-have predicted the position of the Ne+ 1s hole state at E0 = 870.4 eV above the Ne ground state. It has already been shown that the real energy corresponding to the localized component of the autoionizing state is stable under rotations of the function space describing it. Therefore, the earlier E0 can be incorporated into the present calculation in the complex plane. The shift due to the additive contribution of the IAPA is found to be - 0.09 eV. When this is added to E0, the final E = 870.3 eV is in excellent agreement with experiment [870.3 eV; T. D. Thomas and R. W. Shaw, Jr., J. Electron. Spectrosc. Relat. Phenom. 8, 45 (1976)].
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  • 62
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    International Journal of Quantum Chemistry 26 (1984), S. 45-53 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Consciousness is defined as a “response potential” and is stated to be present in all modalities of physical universe. Given this, upon the gathering of interacting complex systems, new functional ensembles bearing “mind”-like or “mindal” properties arise. These properties are delineated. They would arise in a coupled system by producing an “order” or “action” parameter, allowing for adiabatic elimination of variables and enslavement of subsystems by it. Singularities, space-time asymmetry, and action would irrevocably ensue. An experimentally testable model of “mind” is thus projected.
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  • 63
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    International Journal of Quantum Chemistry 26 (1984), S. 73-86 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 64
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    International Journal of Quantum Chemistry 26 (1984), S. 103-108 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino acid analysis has been performed on the products of four simultaneous separate thermal copolymerizations of a set of 18 amino acids. Four analyses have been performed also on aliquots of one of the products. Standard deviations have been calculated for the analyses of the products of the four separate copolymerizations, and for the four aliquots of one copolymerization. All calculations indicate a high reproducibility in the copolymerization reactions.
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  • 65
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    International Journal of Quantum Chemistry 26 (1984), S. 267-272 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a previous study an energy criterion has been applied for the simplification of the enumeration problem of various conformers of biomolecules. In the present note, the above energy criterion is combined with a spatial criterion that in general leads to a reduction in the size of those domains of biomolecule potential surfaces within which the search for chemically important conformers is warranted. The above model and the conformational domains of primary interest can be formulated in a hyperspherical representation. Advantages and disadvantages of representing biomolecule potential surfaces in terms of hyperspherical coordinates are discussed.
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  • 66
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of three cultured cell lines (NRK, 6M2, and 54-5A4) derived from rat kidney to quench a population of ascorbyl and 2,6-dimethoxy-p-semiquinone free radicals has been investigated by electron spin resonance spectroscopy. The radical scavenging action of normal rat kidney (NRK) cells was the weakest, that of 6M2 cells (reversibly transformed phenotype) was four times stronger than NRK, and that of 54-5A4 cells (irreversibly transformed mutants of 6M2) was 10 times greater than NRK. Free radical quenching experiments were also performed on Chinese hamster ovary (CHO) cells. A much slower scavenging rate was observed for CHO cells of normal phenotype grown in the presence of dibutyryl cyclic AMP than was found for cells of transformed phenotype grown in its absence. The free radical quenching kinetics of the various cell lines studied directly paralleled their state of transformation.
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  • 67
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    International Journal of Quantum Chemistry 26 (1984), S. iii 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 68
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    International Journal of Quantum Chemistry 26 (1984), S. 223-235 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Slater-Koster resolvent formalism of exciton theory, as proposed originally by Takeuti, has been applied to calculate charge transfer exciton states and to investigate hypochromism in polynucleotides. As a first step, spatially well localized ab initio Wannier functions (WFS) are calculated at the Hartree-Fock level using a two-phase (inter- and intramolecular) localization procedure for the Fourier transformation of the Bloch functions. The single particle energies, entering the Green's function of the polymer, are corrected for electron correlation effects with the help of second order Møller-Plesset (MP) perturbation theory. The interelectronic matrix elements, used in the MP calculation as well as in solving the resolvent problem for the excitons, are calculated in terms of the WFS. Singlet- and triplet-excitonic dispersions, oscillator strengths, the possible affects of ions, hydration, and aperiodicity on the exciton spectrum are discussed.
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  • 69
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of reactivity of a guanine in B-DNA toward aflatoxin B1 depends on the base sequence surrounding that purine in the double helix. In order to account for this variability, we have computed the ASIF (accessible surface integrated field) index for the N7 atom (at which the reaction occurs) of guanine in a G—C pair surrounded on both sides by different types of base pairs in a model oligohelix. When the conformation of the helix is maintained in the B-DNA form, the correlation ASIF reactivity is limited. A study is performed showing the influence on the ASIF index of different departures from the regular B-DNA conformation, likely to occur in a double helix. It is shown that the correlation ASIF reactivity can be strongly improved by allowing some local departures from this regular arrangement.
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  • 70
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single-channel studies have shown that there exist a multiplicity of conducting states in Gramicidin A (GA). In an earlier work presented at this symposium, it was proposed that such a multiplicity may be expected from different long-lived side-chain distributions available for the channel molecule. In order to test this hypothesis, Leu5-Gramicidin A was synthesized and the effect of replacing the L · Ala5 residue by L · Leu5 was analyzed. First, molecular mechanics calculations on Leu5-Gramicidin A are presented. Then the single-channel conductance sweeps obtained for Leu5-GA are automatically analyzed in the computer using specifically developed algorithms. The results show a dramatic decrease in the multiplicity of states due to the Leu5 substitution. This experimental result is discussed in the light of structural concepts emerging from molecular mechanics calculations.
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  • 71
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    International Journal of Quantum Chemistry 26 (1984), S. 347-353 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Hamiltonian formulation of chemical kinetics is applied to all closed, single-step, integer-order chemical reactions. In all cases, the dynamics of the Hamiltonian leads to the correct phenomenological rate equation. The relationship between reaction order and the form of the reaction potential is discussed.
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  • 72
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pb2+ specifically cleaves yeast tRNAPhe in orthorhombic crystals at phosphates P18 and P60 in the dihydrouridine (D) and pseudouridine (T) loops, respectively. Although there are three major lead binding sites in the tRNA, it appears that both cleavages are affected by the same lead ion. The P18 site is apparently the same site that is hydrolyzed by Pb2+ in solutions of the tRNA and is the major cleavage site in crystals. It is shown from P32 labeling studies with polynucleotide kinase that the products of Pb2+ cleavage have the 5′-hydroxyls on G18 and C60, and consequently the 3′ phosphates are on D17 and U59. The OH- in the first coordination sphere of the hydroxo complex Pb(OH)+ either directly or through a water molecule abstracts the proton of the 2′-OH of D17. This promotes a nucleophilic attack by 2′-O- on P18 with subsequent cleavage of the P—O5′ ester bond to generate the major Pb2+ cleavage product pG18-A76. The anchoring of the Pb2+ by the T-loop and D-loop residues seemingly provide the right environment for the generation of the hydroxo complex required for the hydrolysis. Additionally the strain of the phosphodiester conformation at P18 enhances the cleavage at that site. The Pb2+-catalyzed cleavage of tRNA exemplifies a mechanism used not only for the hydrolysis of transfer RNA but one potentially used by other RNA-catalyzed reaction utilizing metal ion cofactors.
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  • 73
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    International Journal of Quantum Chemistry 26 (1984), S. 267-291 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We propose a variant of the coupled-cluster (CC) method in which spin orbitals of the reference Slater determinant are optimized in a self-consistent way. This approach is a reformulation of the Brueckner-Hartree-Fock (BHF) method used in nuclear physics and known also as the exact SCF method. We discuss the use of the reference-state determinants built of HF, natural, and Brueckner spin orbitals, with relations among them investigated in terms of the many-body perturbation theory (MBPT). It is shown that the Brueckner spin orbitals emerge as a convenient basis set in the coupled-cluster method and equations that determine these spin orbitals are found. The Brueckner spin orbitals can be calculated as eigenvectors of a certain Hermitian one-electron operator which has a form of the Hartree-Fock operator plus a “correlation potential” depending linearly on two- and three- electron cluster amplitudes. The usual decoupling scheme in the coupled-cluster method leads to a hierarchy of approximations; in the first nontrivial one the three-electron cluster amplitudes are neglected, and the two-electron ones are determined by solving Čižek's CPMET equations. We also analyze the problem of spatial, spin, and time-reversal symmertry in the CC and BHF methods. If (and only if) the reference-state determinant belongs to a one-dimensional representation of a certain symmetry subgroup of the system, the CC operator and the BHF one-electron operator are invariant with respect to this subgroup. Thus the restricted (entirely symmetry-adapted) version of the BHF method can be formulated only for the closed-shell systems. This is done for the above-mentioned approximate BHF method. We discuss also the usefulness of the BHF method in application to extended metallic systems.
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  • 74
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    International Journal of Quantum Chemistry 26 (1984), S. 21-24 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 75
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    International Journal of Quantum Chemistry 26 (1984), S. 61-66 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By use of computer algebra and expansions of orbitals about a single center in spherical harmonics with a matrix representation for the α-function coefficients it is possible to produce formulas for each term of an infinite series that represents the value of a three-center exchange integral. Only seven terms are required to get six decimal digits for triatomic hydrogen. This method is readily generalized to solve all three-center exchange integrals over Slater-type orbitals.
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  • 76
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    International Journal of Quantum Chemistry 26 (1984), S. 407-432 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simulated ab initio molecular orbital (SAMO) method band structures of six fluorinated and six chlorinated polymers derived from linear polyethylene are presented and compared with extended Huckel and CNDO/2 studies and with the results of ESCA spectroscopy.
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  • 77
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    International Journal of Quantum Chemistry 26 (1984), S. 449-455 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The summation of the perturbation series for the hydrogen Zeeman effect using the renormalized series technique is studid. Improved results are obtained compared to those obtained from the unrenormalized series; the method has the advantage of not requiring any information on the largeorder behavior of the perturbation series coefficients.
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  • 78
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    International Journal of Quantum Chemistry 26 (1984), S. 467-481 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two lowest bound excited states of the Be- ion, 1s2 2s2p2 4P and 1s2 2p3 4S0, and their respective thresholds, Be 1s2 2s2p 3P0 and Be 1s2 2p2 3P, and the thresholds of these, Be+ 1s2 2s and Be+ 1s2 2p, have been examined using many-body methods. Here, we present the electron affinities (EAs) or ionization potentials, fine and hyperfine structure, and the electric dipole transition probabilities associated with these states and compare them with existing theory and experiment when available. Based on our new EA, a suggestion is made as to why no negative ion transition has yet been seen in the laboratory.
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  • 79
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    International Journal of Quantum Chemistry 26 (1984), S. 525-536 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We derive theoretical experessions for molecular third-order frequency-dependent susceptibilities which represent dc electric-field-induced second-harmonic generation. Our results are valid also if some of the molecular eigenvalues are degenerate as long as the molecular ground state is nondegenerate. The results are in suitable form for quantitative applications, either to small atoms or molecules or to large organic conjugated or aromatic molecules.
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  • 80
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    International Journal of Quantum Chemistry 26 (1984), S. 601-618 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present results on the energetics of the hydrogen bridges for the Guanine-Cytosine pair obtained in a DNA fragment consisting of three stacked base pairs in the B-DNA conformation. The wave function computations on the 87 atom system are all-electron ab initio SCF-MO computations obtained with a basis set of 1032 primitive gaussian functions contracted to 315. Even if the results are only preliminary, one can tentatively advance conclusions relative to the molecular field effect of stacked base-pairs on the potential energy surface for a hydrogen bond. These computations have been performed with a modified version of our molecular program, which uses an IBM 4341 host and six to ten attached array processors (FPS-164) in parallel. The strategy to convert the program from sequential to parallel is briefly outlined and comparisons with our parallel system are made with a present-day “vector” super-computer. From these studies, we conclude that if one adopts the “parallel” approach presented and tested here, much larger chemical systems than previously are now amenable to all-electron ab initio computations.
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  • 81
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    International Journal of Quantum Chemistry 26 (1984), S. 675-681 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Current computer hardware developments, in particular, vector processing and parallel processing, are likely to open the door for new applications in quantum chemistry. One applied field that is expected to evolve is a computer-based approach to quantum-chemical synthesis design. Whereas some of the computational difficulties still appear formidable, there are reasons to be optimistic: besides the direct impact of computer hardware developments on existing methods, new theoretical approaches such as density functional theory and numerical molecular wave functions may also become feasible. The topological model of energy hypersurfaces, reaction topology, and quantumchemical manifold theory of reacting systems form a possible framework for a global analysis of a set of all reactions involving a fixed set of nuclei and a fixed number of electrons. The apparent bottleneck for the application of the topological method is the actual computation of the catchment regions (open sets) of reaction topology Tc. In this study some properties of catchment region boundaries are described which lead to computational simplifications. Whereas the ultimate goal of the proposed analysis is to serve as an aid in future quantum-chemical synthesis planning, nonetheless, the boundary networks and sum rules developed in this study may also be of some immediate interest in local surface analysis.
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  • 82
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    International Journal of Quantum Chemistry 26 (1984), S. 709-717 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixed-node quantum Monte Carlo (QMC) method is used to obtain the classical barrier height for the H + H2 exchange reaction. Using a spin-restricted, single-determinant trial function ΨT, the authors find that the reaction barrier Eb is less than 9.69 ± 0.25 kcal/mol. This mean value is below the calculated energy barrier obtained by Liu in the most extensive CI calculations on this system. Furthermore, the QMC saddle-point energy of - 1.65903 ± 0.00040 hartrees at the CI-determined geometry lies 0.00027 a.u. (0.17 kcal/mol) below Liu's best CI value. Finally, spinrestricted and spin-unrestricted single-determinant trial functions are contrasted. Although the variational energy 〈ΨT|H|ΨT〉 for an SCF ΨT must be lower for the unrestricted case, this is not true generally for QMC. In fact, we show that if the unrestricted SCF ΨT has the lower QMC energy, then there exists another spin-restricted, single-determinant ΨT whose QMC energy is lower than the QMC energy of the spin-restricted SCF ΨT.
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  • 83
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    International Journal of Quantum Chemistry 25 (1984) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 84
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    International Journal of Quantum Chemistry 25 (1984), S. 63-68 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The autoionization widths of levels 1s 2s 2pjJ, 1s2s2 2S1/2, and 1s2pj2pj′ J have been calculated for ions with Z = 6-30. The calculation has been carried out in intermediate coupling. The decay amplitudes have been calculated in a relativistic approximation.
    Additional Material: 1 Ill.
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  • 85
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most of the existing calculations of relativistic effects in many-electron atoms or molecules are based on the Dirac-Coulomb Hamiltonian HDC. However, because the electron-electron interaction mixes positive- and negative-energy states, the operator HDC has no normalizable eigenfunctions. This fact undermines the quantum-theoretic rationale for the Dirac-Hartree-Fock (DHF) equations and therefore that of the relativistic configuration-interaction (RCI) and multiconfiguration Dirac-Fock (MCDF) methods. An approach to this problem based on quantum electrodynamics is reviewed. It leads to a configuration-space Hamilton H+U which involves positive-energy projection operators dependent on an external potential U; identification of U with the nuclear potential Vext corresponds to use of the Furry bound-state interaction picture. It is shown that the RCI method can be reinterpreted as an approximation scheme for finding eigenvalues of a Hamiltonian H+U, with U identified as the DHF potential; the theoretical interpretation of the MCDF method needs further clarification. It is emphasized that if U differs from Vext one must consider the effects of virtual-pair creation by the difference potential δU = Vext - U; an approximate formula for the level-shift arising from δU is derived. Some ideas for dealing with the technical problems introduced by the projection operators are discussed and relativistic virial theorems are given. Finally, a possible scheme for adapting current MCDF methods to Hamiltonians involving projection operators is described.
    Additional Material: 3 Ill.
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  • 86
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single-configuration relativistic Hartree-Fock values of the first ionization potentials for Cu through Kr7+, Ag through I6+, and Au through Pb3+ are computed in “frozen” and “relaxed core” approximations with and without allowance for core polarization. Effects of polarization of the atomic core by the valence electron are included by introducing a polarization potential in the one-electron Hamiltonian of the valence electron. The core polarization potential depends on two parameters, the static dipole polarizability of the core α and the cut-off radius r0, which are chosen independently of the ionization potential data. It is demonstrated that by including the core polarization potential with α and r0 parameters, which are simply chosen instead of being empirically fitted, it is still possible to account, on the average, for at least 70% of the discrepancy between the single-configuration relativistic Hartree-Fock ionization potentials and the experiment, a discrepancy usually ascribed to the contribution of valence-core electron correlations, and to bring the theoretical ionization potentials to an average agreement with experiment of around 1%. It can be concluded from this study that for low and medium Z elements the core polarization dominates for neutral systems or systems in low ionization stages, whereas for highly ionized systems the relativistic effects prevail. For heavy elements, however, the core polarization influence is comparable to the relativistic one only for neutral systems, whereas for ions the relativistic effects are overwhelmingly predominant.
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  • 87
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    International Journal of Quantum Chemistry 25 (1984), S. 423-443 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of bond length alternation in linear extended systems with conjugated double bonds is examined on a simple cyclic polyene model using finite-order many-body perturbation theory. Three different partitionings of the model Hamiltonian are employed, namely the Hückel, Møller-Plesset, and Epstein-Nesbet partitionings. The dependence of correlation energy on bond length alternation is examined in each case, showing an almost constant behavior of Møller-Plesset and Epstein-Nesbet perturbation energies in contrast to a strong dependence on distortion, favoring undistorted structures, for the Hückel perturbation and UHF correlation energies. The origin of an unphysical character of the Hückel perturbation theory and the inappropriateness of the UHF approach for the problem considered are pointed out. The second- and third-order Møller-Plesset and also the second-order Epstein-Nesbet perturbation theories yield results which are similar to those obtained with the RHF method and which clearly favor the bond length alternating structures, leading to the bond length distortion of about 0.045 Å and to the stabilization energy per site (relative to the equidistant geometry) of about 0.03 eV.
    Additional Material: 9 Ill.
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  • 88
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    International Journal of Quantum Chemistry 25 (1984), S. 445-445 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 89
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 483-491 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The limitations arising from the use of a frozen orbital approximation applied to 3s and 3p electrons of the iron atom are investigated at the CI level.
    Additional Material: 3 Tab.
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  • 90
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 553-601 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This is the first paper in a series of three directed toward the evaluation of spin-dependent Hamiltonians directly in the spin-orbit basis. In this paper we present a new and complete derivation of the matrix elements of the U(n) generators in the electronic Gel'fand basis. The approach employed differs from previous treatments in that the matrix elements of nonelementary generators are obtained directly. A general matrix element formula is derived which explicitly demonstrates the segment level formalism obtained previously by Shavitt using different methods. A simple relationship between the matrix elements of raising and lowering generators is determined which indicates that in CI calculations, only the matrix elements of raising generators need be calculated. Some results on the matrix elements of products of two generators are also presented.
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  • 91
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 653-666 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unitarily invariant decomposition of Hermitian operators is performed by means of Lie algebra.
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  • 92
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 707-713 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new derivation is given for the Waller-Hartree-Fock double-determinantal spatial wave function. One starts from the single-determinant wave function in which a orbitals are doubly occupied, and decomposes it into a sum of products of spatial and spin functions. The spatial product of the first genealogical spin eigenfunction is a double-determinantal function. The derivation is based on the simple form of U1ƒ(P) when the representation matrix is obtained from the genealogical spin eigenfunction.
    Additional Material: 1 Ill.
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  • 93
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 715-721 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Expressions for the second-row nuclei chemical shifts calculation using a CNDO-SCF wave function are outlined. In collating it with the Pugmire and Grant's equations, a term with a changed sign appears. Both sets of equations are applied to a study of carbon-13 chemical shifts in alkanes down to C7; results are interpreted with aid of the Lindeman-Adams' empirical equation. Expressions proposed are confirmed for an excellent agreement with experimental data.
    Additional Material: 1 Tab.
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  • 94
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent effects on different transmission mechanisms of spin-spin coupling constants are analyzed from a theoretical viewpoint. Medium effects are introduced using the solvaton model, and the decomposition of coupling constants in σ- and π-electron transmitted components is accomplished with the PRMO method. Trends thus obtained are in fairly good agreement with experimental findings reported in the literature. In all types of couplings studied in this work, σ and π components show opposite behavior when increasing the polarity of the solvent.
    Additional Material: 3 Ill.
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  • 95
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    International Journal of Quantum Chemistry 25 (1984), S. 603-633 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we present a derivation of the U(n) adjoint coupling coefficients for the representations appropriate to many-electron systems. Since the states of a many-fermion system are to comprise the totally antisymmetric Nth rank tensor representation of U(2n), the work of this paper enables the matrix elements of the U(2n) generators to be evaluated directly in the U(n) × U(2) (i.e., spin orbit) basis using their transformation properties as adjoint tensor operators. A connection between the adjoint coupling coefficients, as derived in this paper, and the matrix elements of certain (spin independent) two-body operators is also presented. This indicates that in CI calculations, one may obtain the matrix elements of spin-dependent operators from the known matrix elements of certain spin-independent two-body operators. In particular this implies a segment-level formula for the matrix elements of the U(2n) generators in the spin-orbit basis.
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  • 96
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 645-651 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A constructive approach for deriving the approximating quasiparticle energy density functional is proposed. As a matter of fact, the proposed approach is the direct development of the Kohn-Sham quasiparticle concept and the Levy-Valone approach. The approach presented takes into account a pseudopotential character of the exchange-correlation part of the density functional and results in a system of functional equations to obtain ground-state energies of many-electron systems.
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  • 97
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    International Journal of Quantum Chemistry 25 (1984), S. 881-890 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Compact, convenient expressions for the electron density are derived using a fitting functional. Results are given for H2O, CH4, HF, NH3, and PH3, and show the accuracy obtainable using differing numbers of functions on each center. The definition of an atomic charge using these expressions is discussed and it is shown that the Bader virial-partitioning definition, in which the density is integrated over a volume around each nucleus, leads to convergent results.
    Additional Material: 8 Tab.
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  • 98
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 915-928 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The generalized Hellmann-Feynman and curvature theorems are derived for the generalized Sturm-Liouville-type eigenvalue equation which is widely encountered in many branches of physics. In classical mechanics, the Sturm-Liouville eigenvalue equation primarily arises from applying the theory of small oscillations to vibration problems while, in quantum mechanics, the most important example is the time-independent Schrödinger equation. The generalized theorems, respectively, provide simple useful expressions for the first and second λ derivatives of the eigenvalue where λ is an arbitrary real parameter appearing in the eigenvalue equation. These results, which apply to both classical and quantal systems, include as special cases the well-known quantum mechanical Hellmann-Feynman and curvature theorems for the time-independent Schrödinger equation, thus unifying the formalism. This connection between classical and quantum mechanics is of interest per se, and also because classical eigenvalue equations find application in the treatment of some quantum chemical problems. Two derivations of both generalizations are presented, the first proof applying to exact and Rayleigh-Ritz (linear variational) solutions of the eigenvalue problem, and the second, more general one, to arbitrary optimal variational as well as exact solutions. Necessary and sufficient conditions for the validity of the results are discussed. To demonstrate the insight they afford, several applications of the theorems in conjunction with perturbation theory are described.
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  • 99
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    International Journal of Quantum Chemistry 25 (1984), S. 965-1002 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In connection with spin adaptation in many-body perturbation theory, this paper reexamines the use of spin graphs in view of a Hugenholtz-like representation where both the orbital and the spin parts coexist. Together with the idea of essentially distinct diagrams, this representation leads to an economic handling of spin adaptation. As a side issue, the appropriate generalization of the Epstein-Nesbet partitioning for spin-adapted perturbation theory is obtained. Compact formulas up to fourth order of the ground-state energy, and up to third order for excitation energies and ionization potentials are given.
    Additional Material: 10 Ill.
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  • 100
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 1045-1054 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unitarily invariant decomposition of Hermitian operators for a boson system is performed by means of the symmetry of group SO(2, 1) and the decomposition is also closely related with Lie algebra.
    Type of Medium: Electronic Resource
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