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  • 1980-1984  (327)
  • 1983  (327)
  • Atomic, Molecular and Optical Physics  (251)
  • Gas chromatography
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 54 (1983), S. 311-321 
    ISSN: 1432-0738
    Keywords: Toxaphene ; Distribution ; Mice ; Autoradiography ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Series of female virgin and pregnant albino mice were i.v. injected with14C-labelled- or unlabelled toxaphene (16 mg/kg b.w.). After survival times ranging from 1 min to 32 days the toxaphene distribution in the body was studied using whole-body autoradiography and capillary gas-chromatography. Autoradiographic studies have shown that after an initial accumulation in the liver, brown fat, lung, brain, kidney, and ovaria (corpora lutea) there was a gradual redistribution of radioactivity to the white fat within 4 h postinjection. The labelling was then decreasing rapidly and only negligible amounts of the radioactivity were present in the adipose tissue after 32 days. In the fetus only the liver and adrenals showed a distinct labelling. A specific and persistent accumulation of the label was detected in some zones of the adrenal cortex suggesting a possible direct interference of toxaphene with adrenal steroid hormone synthesis. The gas chromatographic pattern of toxaphene-derived residues in the tissue samples resembled that of the technical toxaphene, but was changing in different tissues with the time. The liver chromatograms indicated more extensive formation of metabolites.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 53 (1983), S. 101-108 
    ISSN: 1432-1246
    Keywords: Biological exposure test ; Exercise ; Gas chromatography ; Hippuric acid ; Humans ; Isotachophoresis ; Laboratory exposure ; o-Cresol ; Rest ; Toluene ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The urinary excretion of hippuric acid and o-cresol was studied after respiratory exposure of human volunteers to approximately 80 ppm (306 mg/m3 ± SD 13) of toluene for 2 h under different work loads (0, 50,100, 150 W, respectively, during 30-min periods). The diet before and after exposure varied. An isotachophoresis method for the determination of hippuric acid is described. The correlation between the total urinary excretion, excretion rate and concentration of hippuric acid, and the respiratory uptake of toluene was poor or non-existing. The same was true for the excretion of o-cresol, which 4 h after exposure was concluded amounted to 0.03–0.26% of the toluene uptake. Thus, after a short-time exposure neither metabolite proved to be a reliable measure of individual toluene uptake at varying workloads or food intake in combination with low exposure levels.
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  • 3
    ISSN: 1432-1238
    Keywords: Gas chromatography ; Head-space analysis ; CCl4 intoxication ; Hyperventilation therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A head-space gas chromatographic method for the determination of carbon tetrachloride in human blood is described. Standard samples with 0.5 ml whole blood containing different concentrations of CCl4 were analyzed at column temperatures ranging from 50° to 90°C. Advantages of this method include high sensitivity, simplicity in handling, rapid achievement of reliable results, accuracy and low costs. The practicability of this analytical method was studied in a patient following suicidal oral ingestion of a lethal dose of carbon tetrachloride.
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  • 4
    ISSN: 1432-2072
    Keywords: Halazepam ; Desmethyldiazepam ; Benzodiazepines ; Pharmacokinetics ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Halazepam and its major metabolite desmethyldiazepam (DMDZ) can be reliably quantitated in human plasma following single doses of halazepam. After addition of appropriate internal standards, halazepam and DMDZ are extracted directly into an organic solvent at physiological pH. The organic extract is separated, evaporated to dryness, reconstituted, and directly chromatographed using a 50:50 methyl:phenyl silicone column (SP-2250) and an electron-capture detector. After a single 40 mg oral dose of halazepam, the parent compound appears in plasma only transiently and at low levels. DMDZ appears in higher concentrations and is slowly eliminated. During multiple-dose therapy with halazepam, DMDZ will be the major active substance in blood.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 34 (1983), S. 20-26 
    ISSN: 1570-7458
    Keywords: Dioryctria abietella ; Cone pyralid ; Lepidoptera ; Pyralidae ; Sex pheromone, (Z,E)-9,11-tetradecadienyl acetate ; Single sensillum recordings ; Electroantennography ; Gas chromatography ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'analyse en chromatographie gazeuse associée à une détection électroantennographique a montré que l'acétate (Z,E)-9,11-tétradécadiényle (Z,E)-9,11–14:Ac est l'un des composants de la phéromone de Dioryctria abietella Schiff (Lepid.: Pyralidae). Couplage chromatographie en phase gazeuse spectrometrie de masse a montré la présence d'acétate tétradécadiényle avec un spectre de masse et un indice de rétention identiques au Z,E-9,11–14:Ac Un récepteur cellulaire sensible à la fois au Z,E-9,11–14:Ac et à un extrait de la femelle a été identifié sous l'antenne du mâle. Les analyses des antennogrammes et de la cellule isolée ont étayé la caractérisation du composant de la phéromone comme étant Z,E-9,11–14:Ac. Un récepteur cellulaire additionnel sensible à l'acétate (Z.)-9-tétradécadiényle et à l'acétate (Z.E.)-9,12-tétradécadiényle a été trouvé sur l'antenne du mâle, mais il n'était pas activé par l'extrait de la femelle. Sur le terrain Z,E-9,11–14:Ac, présenté seul, attirait des nombres importants de mâles de D. abietella. L'addition de l'acétate (Z)-9-tétradécényle a inhibé l'attraction des mâles par les pièges.
    Notes: Summary Gas chromatographic analyses coupled with electro-antennographic detection indicated that (Z,E)-9,11-tetradecadienyl acetate (Z,E-9, 11–14:Ac) is a pheromone component of the cone pyralid Dioryctria abietella. Gas chromatographic-mass spectrometric analyses confirmed the presence of a tetradecadienyl acetate with mass spectrum and retention index identical to Z,E-9,11–14:Ac. A receptor cell sensitive to both Z,E-9,11–14:Ac and the female extract was identified on the male antenna. An additional receptor cell sensitive to (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate was found on the male antenna but was not activated by the female extract. In the field Z,E-9,11–14:Ac presented alone attracted significant numbers of male D. abietella. Addition of (Z)-9-tetradecenyl acetate inhibited the attraction of males to traps.
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; Immobilized liquid phases ; Thick-film columns ; GC-FTIR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The performance of a column prepared with an immobilized (chemically bonded) methylsilicone phase having a film thickness of 5μm is investigated in detail. Due to their high sample capacity, such columns are particularly useful when directly coupling gas chromatography with spectroscopic techniques such as Fourier-transform infrared spectroscopy. Thick-film columns can even be used with thermal conductivity detectors.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 241-243 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Detectors ; Flame ionization detector ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On the occasion of the 25-year anniversary of its invention, this article summarizes the events which led to the development of the flame ionization detector.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 472-476 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid stationary phase ; Liquid phase bleeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The theory of the evaporation of the liquid stationary phase is elaborated and experimentally verified. On the basis of this theory the role played by the losses in the amount of liquid phase present is quantitatively determined. General techniques are examined which minimize the losses; these techniques are based on saturating the incoming carrier gas with liquid phase vapours and raising the pressure of the carrier gas in the column, e.g. by connecting a capillary to the column outlet in order to offer resistance to the gas flow. The application of these techniques ensures stable performance of the gas chromatographic columns using a volatile liquid phase.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 33-36 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preparative scale chromatography ; Capacity ; Dual-step separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The capacity of dual-step preparative chromatographic separation systems is considered. It is shown that dualstep separation makes it possible to enhance the capacity of preparative installations as compared with single- and dual-stage purification of the compounds.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 418-420 
    ISSN: 1612-1112
    Keywords: Separation of metal chelates ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A very good separation of the acetylacetonate of AL-(III), Cr(III) and Co(III) has been obtained by gas chromatography, on a column containing OV-17 silicone oil as the stationary phase.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 421-425 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Purge and trap sampling ; Cryogenic focussing ; Water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The most important operating parameters of a commercial purge and trap GC apparatus have been investigated. Band broadening problems arising from the slow desorption of compounds from the Tenax trap have been overcome by cryogenic focussing at the beginning of the column. Good results have been obtained with both packed and capillary columns. The sensitivity of the technique is sufficient to detect benzene in water at concentrations below 1μg kg−1 (1 ppb).
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 65-69 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Oxygenates ; Fused-silica capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method of analysing gasolines that contain oxygenates has been developed. The method uses a single fusedsilica capillary column and gives quantitative data for the oxygenates and the hydrocarbons in one analysis.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 600-604 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Alkyl benzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The additivity concept in the retention index system of Kovats has been examined for a series ofn-alkylbenzenes and theiro- andp-monosubstituted nitro-, amino-, and chloro-derivatives. Anomalous behaviour is exhibited by the first three members of the series on both polar and non-polar stationary phases. For addition of a methylene group ton-propylbenzene or ap-substituted derivative, it is found that the retention increment, Δl CH2, approaches 100 units. However, the strong inductive effect of the group in the ortho position and the steric effects apparent in ano-substituted alkylbenzene lead to large variations of retention increment upon addition of-CH2-to the alkyl chain. A study ofn-alkylbenzene retention on Apiezon L and Carbowax 20M over a wide range of temperatures has verified the linearity of the retention increment with temperature and has revealed that this gradient increases with increasing carbon side-chain length for the first few members of the series, thereafter becoming constant. Functional retention increments, Δlx, for substitution of nitro-, amino- and chloro-groups into the benzene ring are given.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 191-194 
    ISSN: 1612-1112
    Keywords: Thermal treatment of MgO and MgCO3 ; Adsorption properties ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The changes in the chromatographic properties of MgO and MgCO3 due to thermal treatment was investigated. The experimental results show that thermally treated MgO and MgCO3 can be used as stationary phase for the gas-adsorption chromatography of hydrocarbon mixtures.
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  • 15
    ISSN: 1612-1112
    Keywords: Esterification in aqueous solution ; n-Butyl esters of fatty acids ; Gas chromatography ; Fatty acid analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The esterification of C1−C8 fatty acid in aqueous solutions and in the presence of sulfuric or hydrochloric acid and with n-butanol is described. It has been established that the esterification can be used for the quantitative determination of these fatty acids in the concentration ratio range of [H2O]/[n-BuOH]=0.01–5.3. In the concentration ratio range of 0.01–0.8 the water present does not interfere. In the concentration range of above 0.8 anhydrous sodium sulfate is used for binding the water, in the amount of [Na2SO4.anh.]/[H2O]≥0.2.
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  • 16
    ISSN: 1612-1112
    Keywords: Esterification in aqueous solution ; iso butyl esters of C1–C20 fatty acids ; Gas chromatography ; Fatty acid analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary C1–C20 carboxylic acids have been esterified in aqueous solutions with i-butanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been established that esterification in the concentration range of [H2O]/[i-BuOH]=0.01–10.3 can be utilized for the quantitative determination of these carboxylic acids. The presence of water does not interfere in the range of [H2O]/[i-BuOH]=0.01–1.03. In the cases of [H2O]/[i-BuOH]〉1.03, anhydrous sodium sulfate has been used for binding the water, in an amount of [Na2SO4]anh./[H2O]≥0.2.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 44-46 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Natural gas analysis ; Poropak N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple gas chromatographic method is described for the rapid analysis of natural gas using thermal conductivity detectors and programmed-temperature operation of a single Poropak N column. The method permits the determination of nitrogen, carbon dioxide and hydrocarbons containing one to seven carbon atoms.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 553-559 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; Immobilized liquid phases ; Thick-film columns ; Diffusion coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of the liquid phase film thickness in open-tubular (capillary) columns on the individual resistance-to-mass-transfer terms and on the overall column efficiency is examined from the theoretical point of view. Methods for the calculation of the diffusion coefficients are discussed.
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  • 19
    Electronic Resource
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    Springer
    Chromatographia 17 (1983), S. 691-692 
    ISSN: 1612-1112
    Keywords: Dichlorophenol isomers ; Sodium benzenesulfonate ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is difficult to separate all the dichlorophenol isomers as free phenols by gas-liquid chromatography. However they were effectively separated on 4,4′-dimethoxyazoxybenzene (liquid crystal), and all the isomers were separated appreciably well on sodium 1-naphthalenesulfonate, 2-naphthalenesulfonate and dodecylbenzenesulfonate.
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  • 20
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Trace analysis ; GC-concentration ; Enrichment factor ; Theoretical evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Based on gas chromatographic retention data obtained on a given adsorbent and at a given trap efficiency at different temperatures new equations are proposed for the evaluation of the enrichment factor. These equations are suitable under various preconcentration conditions such as: equilibrium saturation, complete trapping and permissible losses. Compared to known expressions for the evaluation of the enrichment factor the equations suggested consider the band broadening of the impurity in a trap causing a loss of the substance at the adsorption stage and dilution of the sample during desorption when the desorbed impurities are directed into the gas chromatographic column without intermediate freezing out in an graphic column without intermediate freezing out in an empty tube. The new equations may be used to select the optimum preconcentration conditions providing the necessary sensitivity.
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  • 21
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    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 269-284 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid chromatography ; Phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas and high-performance liquid chromatographic methods in the analysis of phenols are reviewed. Among the great number of phenolic compounds analyzed, alkylphenols, chlorophenols, dihydroxy- and trihydroxybenzenes and biphenols are chiefly considered. The advantages and drawbacks of the methods are discussed, quoting the most important work. Relationships between the structural characteristics of phenols, the stationary phase structure, the mobile phase composition and the retention data are treated. Typical examples of the conditions for GC and HPLC analysis are summarized in tables. The literature comprises over 270 references, most of them recent.
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  • 22
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Average molecular polarizability ; Retention index ; Polycyclic aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Kováts retention indices of 10 polycyclic aromatic hydrocarbons were determined on SE-30, OV-101, SE-52, OV-7 and OV-17 stationary phases. A significant correlation has been found between the retention indices and the average molecular polarizabilities of the analyzed substances. Equations were derived for the direct determination of the average molecular polarizabilities from the retention index values. The influence of the temperature on this relationship is also indicated.
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983) 
    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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  • 24
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 325-338 
    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: Interaction energies ΔE accompanying the formation of van der Waals (VDW) systems may be estimated by means of the formula ΔE = ΔESCF + BSSE + ED(r-6, r-8, r-10), where BSSE is the basis set superposition error and ED is the dispersion energy in the expanded form. Twenty one stationary points were located on the potential energy surfaces of hydrogen-bonded complexes; of those, 18 were local minima and 3 were saddle points. Thermodynamic characteristics calculated on the basis of molecular constants, quantum chemically generated, were obtained for 12 hydrogen-bonded complexes and for competition equilibria between VDW molecules. The role of the VDW forces in some rate processes and in a prototype of enzyme-substrate interactions is outlined. In connection with enzymic catalysis, the intramolecular discrimination in 1,2-difluorohydrazine, and the stability of hydrogen-bonded complexes in a cation field is discussed.
    Additional Material: 6 Ill.
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  • 25
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), 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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  • 26
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 341-363 
    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 LCAO Hamiltonian is performed in terms of a “mixed” formulation of the second quantization for nonorthogonal orbitals, compressing the different interactions to one- and two-center terms as far as possible by performing appropriate projections. For this purpose an operator of atomic charge is also introduced, the expectation values of which are the Mulliken gross atomic populations on the individual atoms. The LCAO Hamiltonian is decomposed into terms having different physical meaning and significance: (i) sum of effective atomic Hamiltonians; (ii) the electrostatic interactions in the point-charge approximation; (iii) the electrostatic effects connected with the deviation of the actual charge distribution from the pointlike one; (iv) two-center overlap effects; (v) finite basis (“counterpoise”) correction terms related to the individual atoms; and (vi) similar finite basis correction terms with respect to the two-center interactions. Only terms of types (i) to (iv), containing no three- or four-center integrals, are considered as having physical significance. Based on the analysis of the Hamiltonian, an energy partitioning scheme is developed, and explicit expressions are given for one- and two-center (and basis extension) components of the SCF energy. The approach is also applied to the problem of intermolecular interactions, and an explicit formula is given permitting calculation of the “counterpoise” part of the supermolecule energy by properly taking into account that it depends not only on the extension of the basis, but also on the occupation of the additional orbitals in the intervening molecule - a factor completely overlooked in the usual scheme of calculations.
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  • 27
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 369-377 
    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: Quantum mechanics is a remarkable formalism for studying problems in the microscopic domain, and nobody has reasonably contested its power. Nevertheless, in spite of the many interpretations which have been proposed, its true meaning is far from being clear. The aim of this preliminary paper is to show that it is possible to conceive within a classical framework an interpretation of quantum mechanics and to make its limits of validity precise.
    Additional Material: 1 Tab.
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  • 28
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 679-686 
    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: Heats of atomization for a range of conjugated molecules containing nitrogen or oxygen are calculated by a semiempirical method that combines some features of both the MO and VB theories. The π ground state of each conjugated molecule is represented as a linear combination of Kekulé structures. Unlike in the VB theory, each Kekulé structure is a determinant containing bond orbitals. Here experimental heats of atomization are reproduced approximately as well as by the more sophisticated SCF-MO approach. The use of this method is, however, much simpler since it amounts to a single diagonalization of a matrix of the order equal to the number of Kekulé structures only.
    Additional Material: 2 Ill.
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  • 29
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 663-678 
    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: Nonlinear equations are important for the description of dissipative processes and soliton-related phenomena. One of the principal aims of the theory of symmetry breaking in quantum mechanics is to provide a systematic method for introducing interactions which reduce the symmetry of a system. Such a method is applied here to compute the general form of the symmetry-breaking interaction F(x,t, Ψ, Ψ*) for the time-dependent Schrödinger equation in one spatial dimension \documentclass{article}\pagestyle{empty}\begin{document}$$ \left[{\partial _{xx} + 2i\partial_t - 2g_2(t)x^2 - 2g_1(t)x - 2g_0 (t)} \right]\psi (x,t) = F(x,t,\psi,\psi *). $$\end{document} For F = 0, it has been shown that the Lie algebra of space-time invariances of this equation is S1 = s1 (2,IR)□w1, the Schrödinger algebra. Following the method of Boyer, Sharp, and Winternitz, all conjugacy classes of subalgebras of S1 are given. For each subalgebra, the most general form of the interaction term F(x,t, Ψ, ψ*) is constructed. The potential F then reduces the symmetry from S1 to the considered subalgebra. Furthermore, the one-dimensional subalgebras of S1 obtained above partition S1 into orbits of operators. To each orbit there corresponds a coordinate system in which the above equation separates variables. A partial resolution of the solutions of the above equation has been obtained by exploiting this relation. The algebraic approach to symmetry breaking yields a rich variety of interaction terms F, which appear to generalize the nonlinear Schrödinger-Langevin-Kostin equation for nonconservative systems and the so-called nonlinear Schrödinger equation. A criterion in terms of the existence or nonexistence of Bäcklund transformations is conjectured in order to distinguish between dissipative and soliton equations.
    Additional Material: 4 Tab.
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  • 30
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 709-712 
    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: Following the conjecture of Fröhlich that the Bose condensation of phonons is the dominant biological effect, Wu and Austin derived from the Fröhlich Hamiltonian an expression for the relaxation time which is inversely proportional to the temperature by using the technique of Green's function. In this paper, we have generalized the Wu and Austin expression by improving their approximations with the superconducting canonical transformation and obtained the relaxation time depending exponentially on the inverse temperature. Moreover, we have checked our expression by using a different method based on the “continued fraction expansion” and also employed this technique to derive the dielectric constant for this system.
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  • 31
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    International Journal of Quantum Chemistry 23 (1983), S. 713-722 
    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 computer-oriented algorithm is developed for identification and enumeration of carcinogenic bay regions in benzenoid hydrocarbons. The results are reported for geometrically planar benzenoid systems up to ten fused rings. They fully agree with those obtained in a different way by Balasubramanian et al. The advantage of the proposed method is that we can display all planar benzenoid structures and identify the carcinogenic bays in each of them.
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  • 32
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    International Journal of Quantum Chemistry 23 (1983), S. 723-728 
    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: Calculating the electrostatic potential around the Ser-His-Asp catalytic triad in serine proteinases the very important substituent effect of the buried aspartate is revealed. It is found that the strong Coulomb field of this distant but charged side chain considerably enhances the nucleophilicity of the active serine hydroxyl group. The interpretation of the vital importance of aspartate may replace the “charge-relay” hypothesis which seems to be disproved in the light of recent experiments.
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  • 33
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    International Journal of Quantum Chemistry 23 (1983), S. 729-738 
    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: Quantum chemical studies on interaction of p-benzoquinone and mitomycin C with complementary base pairs have been performed. The empirical potential function and semitheoretical algorithm were applied for estimation of intermolecular interaction energy. Non-negligible intercalation of the quinone ring into fragments of nucleic acid seems to be justified. Extensive calculations on the specificity of mitomycin C intercalation were performed using AGNAS/IMNAS algorithm based on an empirical potential function. No clear preference for intercalation into any kind of base pairs was found.
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  • 34
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    International Journal of Quantum Chemistry 23 (1983) 
    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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  • 35
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    International Journal of Quantum Chemistry 23 (1983), S. 765-778 
    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: Hydration sites of the acetal segment were studied in five of the most stable conformers of 2-methoxy-tetrahydropyran (MTHP) as the first step in the determination of the hydration scheme of glycosides. The intramolecular geometries of a supermolecule formed with MTHP and water were calculated by a PCILO quantum-chemical method. The hydration sites determined can be classified into two groups: (a) individual sites, in which water interacts with one oxygen only, and (b) bridging sites, in which water interacts with both oxygens. The interaction energies of the individual sites are approximately 22 kJ mol-1, and 26 and 29 kJ mol-1 in the bridging sites. An increase of the number of water molecules in the hydration shell of MTHP showed that monohydration of the glycosidic linkage oxygens was most advantageous. Despite of the fact that the hydration shell have various structures in the individual MTHP conformers, the obtained results indicate that the hydration does not operate against the anomeric or exoanomeric effects, i.e., it does not influence the equilibrium of the MTHP conformers in favor of the trans arrangements of a glycosidic bond. Therefore, the experimentally observed stabilization of the trans positions in aqueous solutions should be considered as a result of influence of water being a dielectric continuum.
    Additional Material: 4 Ill.
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  • 36
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    International Journal of Quantum Chemistry 23 (1983), S. v 
    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
    Additional Material: 1 Tab.
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  • 37
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    International Journal of Quantum Chemistry 23 (1983), S. 789-809 
    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: Effective solutions for two difficulties which may be present in MCSCF calculation are discussed: (i) We show how the large configuration state function state expansion case may be handled simply and effectively without the introduction of extraneous projection operators or Lagrange multipliers; (ii) we present a simplified two-electron integral transformation procedure which significantly reduces the operation count (and hence computational efficiency is increased) for second order and particularly for third order MCSCF procedures. The procedures we introduce use some freedom available in the orthogonal complement Cl space and the virtual orbital space to simplify MCSCF calculations.
    Additional Material: 4 Ill.
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  • 38
    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 systematic investigation of momentum densities Π(p), Compton profiles J(q), and internally folded densities B(r) has been made for the ground states of the atoms from H to Kr. The data are presented in reduced form by means of the characteristic momentum p* = q* and length r* = 1/p*, where p* = [J(0)/2πΠ(0)]½. The results indicate that p* and J(0) contain the gross qualitative behavior of the atomic properties in momentum space. They also show that subtle effects over and above the gross scale and size are mostly periodic.
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  • 39
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    International Journal of Quantum Chemistry 23 (1983), S. 821-834 
    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 technique for a simple and efficient treatment of intermolecular interactions is proposed and tested. The method is based on an approximation of the first order SCF term ESCF(1) which is the most structured contribution to the total interaction. ESCF(1) is represented by a site-site potential V of (exp, 1/R)-type, which accounts for the exchange plus penetration and the long range Coulomb forces (by means of a point charge model). The individual contributions to V are obtained by means of combination rules from corresponding site parameters of interacting molecules. The site parameters are consequently molecular and not intermolecular properties and can conveniently be determined by probing a molecule with appropriate test particles. Site parameters are reported for He, Ne, Ar, N2, CO, CO2, CS2, and HCl. Comprisons show close agreement of V with ESCF(1) which in turn is close to ΔESCF if polarization and charge transfer effects are small.
    Additional Material: 4 Ill.
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  • 40
    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 coupled-cluster single and double excitation model (CCSD) is applied to an energy path for the insertion of Be into H2 and compared to the full configuration interaction (FCI) and full valence-multiconfiguration self-consistent field (FV-MCSCF) results. This model problem is a severe test of a single-reference-function correlated method since two configurations are heavily weighted in the FCI description. CCSD is demonstrated to describe the FCI results using a single reference function which, however, changes orbital characteristics along the sampling path. In this case CCSD gives excellent agreement with the FCI results.
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  • 41
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    International Journal of Quantum Chemistry 23 (1983), S. 855-863 
    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: Theoretical models for reductive elimination from transition metal containing molecules have been studied using large scale contracted CI calculations. Four different models were treated, namely, NiH2, PdH2, Ni(CH3)2, and Pd(H2O)2H2, in order to study the effects of adding ligands, exchanging hydrogens with methyl groups, and comparing nickel and palladium. The most interesting result already appeared for the simplest system NiH2. A closed-shell-type 1A1 state with a small bond angle of only 57° is bound compared to Ni and H2 with only a very small barrier for formation. The bond distance is short, shorter than in NiH, and the d orbitals are strongly involved in the binding. The hydrogen atoms bind both to nickel and to each other. With methyl groups rather than hydrogens, this double sided bonding situation is destroyed and Ni(CH3)2 has a negative binding energy with the carbon bonds pointing towards nickel. For PdH2 only a weakly bound complex between an essentially unchanged H2 and Pd was found. The bond distance is very long. Adding H2O ligands to Pd shortens the bond distance and significantly opens up the bond angle. The methods used in the investigation and the chemical implications of the results are discussed.
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  • 42
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    International Journal of Quantum Chemistry 23 (1983), S. 865-874 
    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 Titchmarsh-Weyl theory for a singular second-order differential equation is presented. The equations, however, are arranged such that the theory is immediately applicable to the multichannel formulation. The mathematical basis of the Titchmarsh-Weyl theory (TWT) is outlined and the Titchmarsh-Weyl m function is presented. Relations to the associated Green's function and the spectral function are given. It is shown how some quantities common in scattering theory can be expressed in terms of the TWT. The method of complex rotation is then applied to the TWT to create a complex rotated analog of the Titchmarsh-Weyl theory. This is then extended as exterior complex scaling is introduced. An outline of a proof for the method of exterior complex scaling is presented and some numerical results of the complete theory are given.
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  • 43
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    International Journal of Quantum Chemistry 23 (1983), S. 875-886 
    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 valence-shell vertical ionization potentials of Cl2 were calculated by perturbation corrections to the Koopmans theorem using a traditional effective core potential based on a Phillips-Kleinman derivation and an improved effective core potential obtained by Christiansen, Lee, and Pitzer. Comparison of the results with an all-electron calculation demonstrated the reliability of the Christiansen-Lee-Pitzer effective core potential, which was then used to compute the vertical ionization potentials of ClN3 and ClNCO. The results shed new light in the interpretation of the photoelectron spectra of these molecules.
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  • 44
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    International Journal of Quantum Chemistry 23 (1983), S. 887-890 
    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: The carbene reaction 1CH2 + C2H6 was studied with the semiempirical method SINDO 1. The pertinent transition states and products were obtained by geometry optimization on a CI surface. We find the insertion reaction forming C3H8 greatly favored compared to the double insertion leading to CH4 + C2H4. The result is qualitatively the same for the reaction of the two possible intermediate radicals CH3 and C2H5. The geometries and energies of all transition states are presented.
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  • 45
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    International Journal of Quantum Chemistry 23 (1983), S. 891-904 
    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 MNDO study of molecular geometries, enthalpies, formation, atomization, bond separation, and hydrogenation of a series of unsaturated boron-nitrogen compounds, linear with two and three members and cyclic with three, four, five, and six members are presented. For all these molecules, MNDO calculations are in excellent agreement with available ab initio calculations or experimental data. The high rotational barrier in aminoborane H2BNH2, 30.6 kcal/mol, and the length of bond in iminoborane HBNH, 1.183 Å, imply strong double and triple BN bond character in these two molecules. In the odd membered heterocycles, examination of the molecular geometries and energies of equilibrium states shows that in all cases, the stability of the compounds grows with the number of boron atoms and decreases with that of the nitrogen atoms. Moreover, compared study of the two BN-fulvenes with their homologous hydrocarbon shows that only BN (BB)-fulvene has a polyenic structure similar to that of fulvene.
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  • 46
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    International Journal of Quantum Chemistry 23 (1983), S. 1179-1189 
    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 Möller-Plesset perturbation technique and configuration interaction methods are applied to linear chains of hydrogens in order to analyze the role of electron correlation on equilibrium geometries and binding energies of these systems.
    Additional Material: 1 Ill.
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  • 47
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    International Journal of Quantum Chemistry 23 (1983), S. 1191-1199 
    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: Collective modes of superfluid 3He B have been studied by means of sound attenuation and sound velocity studies. A new sound attenuation peak has been observed in superfluid 3He B at ħω ≈ Δ(T). This peak has been identified with the real squashing mode. Pulse time of flight methods has been used in these studies. At high sound amplitudes, interesting transient effects have been observed which have been tentatively identified with solitonlike behavior.
    Additional Material: 4 Ill.
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  • 48
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    International Journal of Quantum Chemistry 23 (1983), S. 1269-1282 
    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 electrostatic models for ion permeability of membranes are considered. In the first model ions pass hydrated through the membrane and in the second model ions pass unhydrated through a channel lined with polar groups. In both cases it is found that it is not necessary to assume a high macroscopic dielectric constant of the membrane or channel to provide a low enough potential energy of the ion in the membrane. Gating of excitable membranes is considered a special case of electrostatic interaction in membranes. A simple physical model which fits with Hodgkin and Huxley's empirical relation is derived. Finally, we have speculated upon other membrane bound biological phenomena where electrostatic effects may be important.
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  • 49
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    International Journal of Quantum Chemistry 23 (1983), S. 1257-1268 
    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 systematic study, the characteristics of triplet oxene models for alkane, alkene, chloroalkane, and aryl oxidations by the cytochrome P450s have been examined using the semiempirical molecular orbital method MNDO and the formalism of statistical mechanics. Specific model substrates chosen were: methane, ethylene, propene, carbon tetrachloride, chloroform, and toluene. It was found that transition state geometries and activation entropies were reliably predicted, but that an empirical factor was necessary to correct overestimation of activation enthalpies. It was determined that both hydroxylations and epoxidation initiated by a O(3P) atom are nonconcerted; and that oxidations of C—Cl bonds (halosylations) occur by a two-step mechanism similar to hydroxylation. It is shown that the radical mechanisms derived from these studies are consistent with a range of observed properties of cytochrome P450 reactions and provide reasonable explanations for secondary deuterium isotope effects and substituent effects in cytochrome P450 epoxidation of styrenes, suicide inactivation of a P450 enzyme by ethylene, and the characteristics of aerobic CCl4 and CHCl3 metabolism. A triplet oxene mechanism for the initial steps of aromatic epoxidation and hydroxylation is also discussed.
    Additional Material: 6 Ill.
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  • 50
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    International Journal of Quantum Chemistry 23 (1983), S. 1305-1316 
    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 needed in INDO calculations for compounds containing 4f elements were derived and an INDO program suitable for lanthanoid compounds was written and tested. Electronic structure of LnF3 and paramagnetic shift of NMR spectra of LnF85- were studied.
    Additional Material: 9 Tab.
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  • 51
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    International Journal of Quantum Chemistry 23 (1983), S. 1317-1353 
    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 overview is given here of band structure calculations on the fourth and fifth group transition metal monocarbides, mononitrides, and monoxides, published since the review article by Calais [J.-L. Calais, Adv. Phys. 26, 847 (1977)]. Furthermore, the relations of three categories of experimental properties, which allow insight into the electronic structure of the above mentioned compounds, and the results of band structure calculations are discussed. Theoretical predictions are compared with experimental findings. The considered experimental properties are valence band photoemission spectra, valence band x-ray emission spectra, and optical properties.
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  • 52
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    International Journal of Quantum Chemistry 23 (1983), S. 1451-1461 
    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 molecular electrostatic potential of the triple helix poly(dT)·tpoly(dA)·poly(dT) is calculated, and the results are examined in relation to those obtained for its component double and single helical parts. For the double helix presenting the standard Watson-Crick hydrogen bonds, the deepest potentials are formed on the side of the major groove, a situation similar to that observed in the A-DNA duplex. For the double helix presenting Hoogsteen-type hydrogen bonds the deepest potentials lie in the major groove, on the side of the pyrimidine strand. In the triple helix the deepest potentials are located in the major groove in a narrow zone over the thymine bases of the Watson-Crick pair.
    Additional Material: 6 Ill.
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  • 53
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    International Journal of Quantum Chemistry 23 (1983), S. 1469-1478 
    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 for evaluating the function Fm(t) occurring in molecular integrals over Gaussian-type orbitals are reviewed and extended. Formulas based on Bessel function and continued-fraction expansions are analyzed. The recommended evaluation procedures, embodied in a portable computer program, involve Padé approximations for various argument intervals and use recursion in m. The program is economical in storage requirements and faster than those in current use.
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  • 54
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    International Journal of Quantum Chemistry 23 (1983), S. 1463-1468 
    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 continuous-time random-walk theory has been developed for Anderson localization. On a continuous time scale random walks are performed along extended (i.e., propagating) and localized (i.e., trap) states. Complete information of disorder is contained in a distribution function called “hopping time distribution function” ψnm(t), which gives the probability per unit time for transition from state m to state n in time t. The “stay-put” probability P(t = ∞), which is the probability to rediscover an excitation at a site “0” at time t = ∞ if it was there at t = 0, is obtained in terms of ψnm(t). Appropriate forms for ψnm(t) are constructed which are in conformity with the photoconductivity experiments on dispersive transport, and P(∞) are calculated. The results indicate that the entire spectrum consists of three regimes, namely, those of (i) “diffusion,” (ii) “weak diffusion,” and (iii) “no diffusion,” which, respectively, designate the extension, the power-law localization, and the exponential localization of states. The results also shed light on the question of “continuous or discontinuous (?)” transition across the mobility edge.
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  • 55
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    International Journal of Quantum Chemistry 23 (1983), S. 1479-1492 
    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 MO theory of structural polyhedrons is one of the basic subjects closely related to the bonding theory of complex compounds and clusters. A series of valuable papers on this subject have been contributed by Hoffman, Wade, King, and Lauher et al. A method called “group overlap method” for constructing the symmetry orbitals and for calculating the group overlap integrals is proposed. It is hoped that the group overlap method may be used for the qualitative and quantitative MO study of structural polyhedrons.
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  • 56
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    International Journal of Quantum Chemistry 23 (1983), S. 1505-1516 
    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 basic concepts of the Prigogine quantum statistical theory of irreversible processes are discussed in connection with a previous paper by Chatzidimitriou-Dreismann and Lippert. The removal of the “dual role” that the Hamiltonian plays within conventional quantum theory corresponds to the introduction of a star-unitary operator T called “intrinsic time.” The formalism of the previous paper is extended to systems that interact with external fields. A formal specification of T, furthermore, follows from the Lt invariance of the basic equations of motion and its connection with the intrinsic time. As an application to fluorescence spectroscopy, a photon counting experiment is presented. It allows us to detect certain predicted “dynamical” fluctuations in emission spectra. Some current experimental results are reported concerning the resolution of the broad fluorescence band of fluoranthene (dissolved in ethanol) through detection of the underlying finer vibrational structure.
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  • 57
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    International Journal of Quantum Chemistry 23 (1983), S. 1529-1533 
    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: Photoreactions on finely divided semiconductors are discussed. Experimental results on photo-oxidation of CO, isobutane, and NH3 over UV-irradiated n-TiO2 (anatase) particles of different size are discussed. The possibility of using size-quantized films for spectroscopy of adsorbates is also considered.
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    International Journal of Quantum Chemistry 23 (1983), S. 1571-1577 
    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 leading effects of a propagator approach to the calculation of resonance energies is presented. By comparison with ΔSCF results, a simple approximation formula has been developed which contains the main features of the VN-1 potential option and the diagonal Tamm-Dancoff approximation. This result is expected to be a useful guide for further refinements of the many-body aspects of the theory.
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  • 59
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    International Journal of Quantum Chemistry 23 (1983), S. 1589-1595 
    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: From theoretical considerations, three types of coherent excitations of biological systems have been suggested: (i) vibrations of membranes and of proteins with frequencies above 109 Hz; (ii) near static excitation of a highly polar metastable state; and (iii) low frequency periodic enzyme reactions. Recent experimental evidence is discussed.
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  • 60
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    International Journal of Quantum Chemistry 23 (1983), S. 1579-1587 
    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 Bose-Einstein-like ordering was earlier proposed as an important mechanism of energy handling in the living systems. In this regard two questions arise at once: (1) is such ordering feasible at body temperature and (2) what is the time that may be taken for establishing coherence? In this paper we hope to answer and satisfy these two questions.
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  • 61
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    International Journal of Quantum Chemistry 23 (1983), S. 1643-1652 
    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 electron density and the molecular electrostatic potential of the β-carbolines are studied using ab initio STO-3G wave functions. The analysis was done from the point of view of a previous model built with monoamine oxidase substrates and irreversible inhibitors. The results confirm the usefulness of the model and make it possible to propose new precision to the molecular electrostatic potential patterns needed to have monoamine oxidase inhibitory activity.
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  • 62
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    International Journal of Quantum Chemistry 23 (1983), S. 1653-1665 
    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: Rayleigh-Schrödinger perturbation theory for many-electron systems has been rederived by an extension of Löwin's partitioning method in which excited configurations are further partitioned by their orders (two equivalent definitions of the order of a configuration are given). The resulting equations show explicitly how first-, second-, and third-order configurations contribute to the first three orders of perturbative corrections to the ground-state wave function, and the first six orders of corrections to the energy. Because the partitioning is by orders of configurations (rather than level, i.e., single, double, etc., excitations) the formalism is unaffected by the applicability, or nonapplicability, of Brillouin's theorem.
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  • 63
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    International Journal of Quantum Chemistry 23 (1983), S. 1677-1677 
    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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  • 64
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    International Journal of Quantum Chemistry 23 (1983), S. 1679-1681 
    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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  • 65
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    International Journal of Quantum Chemistry 23 (1983), S. 1683-1683 
    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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  • 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 Hel photoelectron (PE) spectra of desmethyldiazepam, diazepam, oxazepam, temazepam, 3-(S)-methyldesmethyldiazepam, 3-(S)-methyldiazepam, 5-methyl-2H-1,4-benzodiazepin-2-one, and benzophenonmethylimine have been measured and analyzed. Their low-energy regions (up to 12.0 eV) have been completely assigned by the composite molecule method using the PE spectra of diphenylmethane, benzophenonmethylimine, acetamide, chlorobenzene, and acetophenonmethylimine to compare the electronic structure of equivalent parts.
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  • 67
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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  • 68
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    International Journal of Quantum Chemistry 23 (1983), S. 1687-1688 
    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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  • 69
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    International Journal of Quantum Chemistry 23 (1983) 
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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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  • 70
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    International Journal of Quantum Chemistry 23 (1983), S. 1693-1693 
    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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  • 71
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    International Journal of Quantum Chemistry 23 (1983), S. 1695-1705 
    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 transition energy and geometry of the lowest excited (nπ*) singlet and triplet states of CO, CS, HNO, H2CO, HFCO, and F2CO molecules are calculated by CNDO/S and CNDO/2-VN-1 potential methods, and the results are compared with those of experimental and ab initio theoretical studies, wherever available. In the calculation of the vertical transition energy, the performance of the CNDO/S method is seen to be generally more satisfactory than that of the CNDO/2-VN-1 potential method, while the reverse is true for the excited-state geometry. The CNDO/S method as such fails to describe the geometry of the excited state, but a combined version (CNDO/S-2) of CNDO/S and CNDO/2, as well as the CNDO/2-VN-1 potential method is fairly successful in this regard.
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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: Many regularities in properties among structurally related compounds are known but a systematic approach to investigate all such cases is rare. A plan is outlined for a systematic study of structural regularities that is based on use of selected graph invariants as prime auxiliary quantities. In this paper carbon-13 chemical shifts in alkanes are examined. Since NMR spectra of paraffins are well understood, the example provides a useful illustration of the approach, introduces basic concepts, and illustrates the kind of the results that the graph-theoretical scheme generates. Differences and similarities between graph-theoretical viewing of the problem of structural regularities and customary direct use of additivities are discussed in some detail.
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  • 73
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    International Journal of Quantum Chemistry 23 (1983), S. 1723-1738 
    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 have performed coordinate rotated configuration interaction calculations on well-studied Feshbach resonances of H- and He- and on 2P shape resonances of Be- and Mg-. The focus of our efforts was the dependence of computed resonance energies on both the quality of the atomicorbital basis and the level of treatment of electron correlation. Our results indicate that great care must be taken to guarantee that a basis is adequate; commonly used quantum-chemistry bases are probably far from satisfactory. Our findings also indicate that a proper treatment of inner-shell orbitals within coordinate rotation calculations is a formidable task. We are therefore encouraged to look carefully for modified coordinate rotation techniques that focus on the active valence-level orbitals and may avoid spurious complex energies arising from improper treatment of inner shells.
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  • 74
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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 nondegenerate finite-order many-body perturbation theory is applied to simple model systems in which the degree of quasidegeneracy can be continuously varied over a wide range. Three ab initio minimum basis set models involving four hydrogen atoms in various spatial arrangements are considered. The results are compared with the exact full configuration-interaction approach, double-excitation configuration-interaction and the coupled-pair many-electron theory.
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  • 75
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    International Journal of Quantum Chemistry 23 (1983), S. 1807-1816 
    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 an n level quantum system there is a relation between each density operator and an element of su (n) Lie algebra. This relation is also established between Cartan's subalgebras and the complete sets of compatible observables. A scalar product is then defined in this algebra in order to introduce orthonormal bases and to simplify many calculations about expectation values of observables. Therefore simple general rules were established which show how to determine (completely or partly), from linearly independent observables, the density operator of the system.
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  • 76
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    International Journal of Quantum Chemistry 23 (1983), S. 1817-1827 
    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 the previous paper we examined, for a quantum system, the relation between its n-dimensional state space and the su (n) Lie algebra. The present paper is devoted to relations between unitary transformations in the state space and orthogonal transformations in Lie's algebra. Two cases can happen. First, the transformations are independently chosen in the two spaces; this amounts to changing the former relation. On the other hand, the relation is maintained and the unitary operators are then related to some of the orthogonal operators. This second case is used to study the evolution operators.
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  • 77
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    International Journal of Quantum Chemistry 23 (1983), S. 1829-1841 
    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 definition of the cyclic polynomial of conjugated hydrocarbons is offered. The combinatorial characteristics of this polynomial are investigated. The most important property of the cyclic polynomial is that it can be used for enumeration of conjugated circuits.
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  • 78
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    International Journal of Quantum Chemistry 23 (1983), S. 1843-1853 
    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 calculations for liquids or solids one often considers a limited cluster of atoms or molecules in the electrostatic field of their environment. In this paper possibilities of improving this model by inclusion of the exchange deformation potential are shown. The reported numerical results for the LiF and NaF molecules as well as for the LiF and NaF perfect crystals indicate the importance of the exchange deformation effects.
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  • 79
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    International Journal of Quantum Chemistry 23 (1983) 
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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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  • 80
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    International Journal of Quantum Chemistry 23 (1983), S. 1855-1867 
    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: Generating functions are constructed and recurrence relations are derived for the number of configurations of any number of particles with an arbitrary elementary spin for both fermions and bosons. Similar results are obtained for the number of configurations specified by the total weight and by the degree of excitation.
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  • 81
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    International Journal of Quantum Chemistry 23 (1983), S. 1969-1972 
    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 performed an analysis of the drug-receptor equilibrium constant, Ki = {QDiRQDi-1QR-1} exp (-Δεi/kT). It is shown that, for a group of nonrotating molecules we may consider the product of the partition functions as constant if log(mass) = constant for all the molecules.
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  • 82
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    International Journal of Quantum Chemistry 24 (1983), S. 25-60 
    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 discuss how the local convergence of Newton-Raphson and fixed Hessian MCSCF iterative models may be rationalized in terms of a total order of convergence in an error vector and a corresponding error term. We demonstrate that a sequence of N Newton-Raphson iterations has a total order of convergence of 2N and that a sequence of N fixed Hessian iterations has a total order of convergence of N + 1. We derive the error terms of a Newton-Raphson and a fixed Hessian sequence of iterations. We discuss the implementation of the fixed Hessian and the Newton-Raphson approaches both when linear and nonlinear transformations of the variables are carried out. Sample calculations show that insight into the structure of the local convergence of Newton-Raphson and fixed Hessian models can be based on an order of convergence and an error term analysis.
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  • 83
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    International Journal of Quantum Chemistry 24 (1983), S. 61-64 
    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: Recently, using the Na atom as an example, Csavinszky has introduced the shell structure into the Thomas-Fermi-Dirac energy-density functional with the Weizsäcker and Hodges gradient expansion corrections to the kinetic energy term. Also recently, two rigorous lower bounds to the Weizsäcker correction in atoms of spherical symmetry have been derived by Gadre and Pathak. The present work investigates the magnitudes of the lower bounds in statistical models of the Na atom with shell structure.
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  • 84
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    International Journal of Quantum Chemistry 24 (1983), S. 65-77 
    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 method for nonadiabatic many-particle quantum-mechanical calculations is described and illustrated for the special case of three particles. The method uses a basis of explicitly correlated Singer-type exponential quadratic function (polymals) of the internal degrees of freedom. Rigorous symmetry states are projected from the basis: linear momentum of the center of mass, total angular momentum, and permutational symmetry under interchange of indistinguishable particles. The nonadiabatic wave functions are interpreted via purely quantum-mechanical criteria of interparticle correlation as measured by average values of powers of interparticle distances and angles. The illustrations are made on H2+ which is easily treated in the Born-Oppenheimer and adiabatic approximations, on helium, muonic helium, and on (e+, e-, e+) which are poorly described in adiabatic methods. The ground and lowest bound excited states of these systems are studied with up to 256 tempered Singer polymals for which we find energies too high by 0.0011 a.u. in H2+, 0.0017 a.u. in muonic helium, 0.0009 a.u. in 4He, and 0.0002 a.u. in (e+, e-, e+); the corresponding relative errors are 1800, 4, 300, and 200 ppm, respectively.
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  • 85
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    International Journal of Quantum Chemistry 24 (1983), S. 79-84 
    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 scheme for calculating expectation values in coupled-cluster wave functions is given. The unlinked terms originating from the norm of the wave function are eliminated. Hermiticity and trace conditions for the density matrices are exhibited in such a way as to guarantee their conservation in any reasonable truncation scheme.
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  • 86
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    International Journal of Quantum Chemistry 24 (1983), S. 85-96 
    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 equilibrium Co—F bond distance and the a1g vibrational frequency of CoF6n- complexes (n = 4, 3, and 2) in crystals were investigated from a theoretical point of view. Ab initio SCF MO calculations were performed for the isolated CoF6n- complexes in order to obtain the potential energy curves against the Co—F distance. These potential energy curves were improved by considering the effect of the surrounding ions. It is shown that the effects of the next-nearest neighbors (eight K+ ions) and the next-next-nearest neighbors (six Co2+ ions) are very important in determining these properties for “ionic” KCoF3 crystal. On the other hand, for Cs2CoF6 crystal, in which the Co—F bond has considerable degree of covalency, the shape of the potential energy curve is almost completely determined by the nonelectrostatic component of the intramolecular interaction of the isolated CoF62- unit.
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  • 87
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    International Journal of Quantum Chemistry 24 (1983), S. 97-111 
    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 Gel'fand-Levitan theory is applied to obtain the exact potential function for an atomic or a molecular system when the solution of the Schrödinger equation with a reference potential which is close to the actual potential is known. With this method one can construct bound state equivalent local potentials, or potentials which, for large quantum numbers, have spectra similar to that of the reference potential. In one-dimensional problems the resulting potentials are not generally symmetric about the origin, even if one starts with symmetric reference potentials. This lack of symmetry is due to the presence of additional terms in the Hamiltonian which are of purely quantal origin, and therefore in any semiclassical treatment become negligible. This observation leads one to investigate the relationship between the spectrum of a given system and the symmetry of the underlying Hamiltonian. Examples are given to show that the dynamical symmetries usually associated with the spectral properties do not necessarily follow from the Gel'fand-Levitan inverse theory, but can be imposed as constraints on the solution. Additional constraints on the form of the two-body wave function also arise from the observable transition rates for atom-molecule collisions and for the interaction of the charged particles in the system with an external electromagnetic field.
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    International Journal of Quantum Chemistry 24 (1983), S. 127-130 
    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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  • 89
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    International Journal of Quantum Chemistry 24 (1983), S. 136-136 
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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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  • 90
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    International Journal of Quantum Chemistry 24 (1983), S. 137-137 
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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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  • 91
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    International Journal of Quantum Chemistry 24 (1983) 
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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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  • 92
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    International Journal of Quantum Chemistry 23 (1983), S. 27-45 
    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 method has been developed to analyzed the bond and current correlation structures of a molecular many-electron wave function. It is shown that the second order density matrix contains information about the bond and current correlations in its off-diagonal components with respect to the indices of orbital basis functions. We break down the off-diagonal correlation functions into five kinds: charge, spin scalar, spin quadrupole, charge spin, and spin polar correlation functions. For a real wave function, the four correlation functions, except for the spin polar one, have only symmetric-symmetric and antisymmetric-antisymmetric components. The former components give site-bond and bond-bond correlations of charges and spins, while the latter components give current-current correlations of charges and spins. The spin polar correlation function has only symmetric-antisymmetric components that give site-current and bond-current correlations of spins. The five off-diagonal correlation functions are expressed in terms of the off-diagonal components of the second order density matrix. The linked off-diagonal correlation functions are defined in that they give dynamical bond and current correlations. The method is applied to the analyses of the bond and current correlations in the low lying exact eigenstates of the PPP Hamiltonian of benzene.
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  • 93
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    International Journal of Quantum Chemistry 23 (1983), S. 65-70 
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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 use of the antisymmetrized geminal power (AGP) consistent reference state for RPA polarization propagator calculations is explored. Illustrative applications to the three lowest electronic states (3B1, 1A1, and 1B1) of the methylene radical are reported with comparisons to other theoretical methods and experiment.
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  • 94
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    International Journal of Quantum Chemistry 23 (1983), S. 71-80 
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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: We have shown that integrals Irs and Jrs which occur in coupled Hartree-Fock perturbation, on a basis of gauge invariant atomic orbitals with the London approximation and neglect differential overlap, can be reduced, by appropriate transformations, to the overlap integral type. The computational program of Srs, Irs, and Jrs integrals is elaborated for Slater-type atomic orbitals. The process proposed presents a double advantage: it is extended over the entire Periodical Table and does not use the analytical formulas of Mulliken.
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  • 95
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    International Journal of Quantum Chemistry 23 (1983), S. 85-89 
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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: An idempotent density matrix in which the orbitals are expanded in Bloch sums is used in the density matrix equation for ρ1(1,1′) to obtain an equation appropriate for a crystal. The general equation is presented as well as its simplification for the single-cell approximation and the nearest-neighbor approximation.
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  • 96
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    International Journal of Quantum Chemistry 24 (1983), S. 241-241 
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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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  • 97
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  • 98
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    International Journal of Quantum Chemistry 24 (1983), S. 185-237 
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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 validity of the Hartree-Fock (HF) approximation in bis(π-pentadienyl)dinickel (1) and in cyclopentadienyl-allyl-cyclobutadiene-dinickel (2) has been investigated by means of the Thouless instability conditions in the computational framework of a variable model Hamiltonian. Singlet, nonsinglet (triplet), and nonreal instabilities in 1 and 2 have been studied as a function of the one-electron resonance integral βμvAB and as a function of the one- and two-center elements of the electron-electron interaction. The one-center integrals of Coulomb (γμvAA) and exchange-type (KμvAA) have been modified by a multiplicative factor; the two-center integrals (γμvAB) have been calculated by means of an exponential interpolation formula with a variable decay amplitude. Additionally the Thouless conditions have been studied for nuclear deformations. The stability domain of the HF solution in the model space spanned by the variable INDO Hamiltonian has been analyzed. The nature of the many-body interactions in the unstable region depends strongly on the parametrization of the model operator. HF instabilities in the high-density region (long-range forces) of 1 have their origin in individual particle-hole fluctuations while negative roots for short-range forces (low-density region) are similar to collective excitations in many-body systems (strong off-diagonal coupling). The opposite behavior is encountered in the Ni complex 2. The physical origin of these different types of correlation processes are analyzed in a simple two-electron two-orbital model. The nature of the HF fluctuations in 1 and 2, the importance of spatial and spin correlation, and the coupling of symmetry breaking of the electronic wave function with nuclear deformations are compared with the nature of phase transitions in solid-state systems.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983) 
    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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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 243-277 
    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 has three aims: (i) To discuss some of the mathematical connections between N-particle wave functions ψ and their single-particle densities ρ (x). (ii) To establish some of the mathematical underpinnings of “universal density functional” theory for the ground state energy as begun by Hohenberg and Kohn. We show that the HK functional is not defined for all ρ and we present several ways around this difficulty. Several less obvious problems remain, however. (iii) Since the functional mentioned above is not computable, we review examples of explicit functionals that have the virtue of yielding rigorous bounds to the energy.
    Type of Medium: Electronic Resource
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