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  • 1965-1969  (258)
  • 1850-1859
  • Physics  (232)
  • Computational Chemistry and Molecular Modeling  (26)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 343-360 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of detailed measurements of osmotic pressure, light scattering, and viscosity of poly(vinyl chloride) solutions are used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl chloride) molecule, and to analyze critically the [η]-M correlations published hitherto.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 1 (1967), S. 421-425 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On a calculé, pour un déterminant de Slater projeté sur un sous-espace de spin défini, les fonctions de densité pour deux électrons, définies par McWeeny.
    Abstract: Die Zweielektronenfunktionen von McWeeny, sind für eine Spin-projizierte Slaterdeterminante berechnet worden.
    Notes: The two-particle density functions introduced by McWeeny are calculated for a spin-projected Slater determinant.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 13-15 
    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.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 1 (1967), S. 675-692 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Les matrices de densité du premier et du second ordre D(N) et D2(N) pour la fonction g(n) = AN[g(1, 2) … g(N - 1, N)] sont emprimées par la fonction même g(1, 2) et par sa matrice de densité D. Dans l'état singulet les fonctions génératices pour les parties spatiales sont simplement liées à la résolvante de l'équation de Fredholm dans laquelle la partie spatiale D sert de noyau. Quelques cas particuliers de g(1, 2) sont considérés. On établit que le nombre de grandes valeurs propres D2(N) ne dépasse pas le nombre de valeurs propres différentes de D. Ainsi c'est la perturbation dans le spectre D qui produit ces grandes valeurs propres.
    Abstract: Die Dichtematrizen der ersten und zweiten Ordnung D(N) und D2(N) für die Funktion g(n) = AN[g(1, 2) … g(N - 1, N)] werden durch die Funktion g allein und ihre Dichtematgrix erster Ordnung D ausgedrückt. Im Singletzustand hangen die erzeugenden Funktionen für die räumlichen Teile dieser Matrizen mit dem Resolventum von Fredholms Gleichung, mit dem räumlichen Teil von D als Kern zusammen. Hier werden einige spezielle Fälle für g(1, 2) betrachtet. Es wurde festgestellt, dass die Zahl der grossen Eigenwerete D2(N) Die Zahl der verschiedenen Eigenwerte von D nicht übersteigt. Somit hat die Degeneration im Spektrum D das Auftreten von solchen grossen Eigenwerten zur Folge.
    Notes: The first- and second-order density matrices D(N) and D2(N) for the function g(n) = AN[g(1, 2) … g(N - 1, N)] are expressed by the g function itself and its density matrix D. In a singlet state the generating functions for spatial parts of these matrices are simply connected with there solvent of the Fredholm equation in which the spatial part of D is a kernel. Some special cases of g(1, 2) are considered. It isestablished that the number of large eigenvalues of D2(N) does not exceed that of different eigenvalues of D. Thus the degeneracy in the spectrum of D causes the appearance of such large eigenvalues.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 1013-1025 
    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: All-electron SCF-LCAO-MO computations for diazomethane, ketene and allene are presented. The basis functions are contracted Gaussian orbitals. Theoretical results are discussed and related to available experimental data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 169-184 
    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 the properties of one version of the least squares (LS) method for the solution of the Schrödinger equation. These properties are exemplified by a number of calculations on the n1S and n3S states of helium, up to principal quantum number three, which are very much more accurate than previous LS calculations on helium. Particular attention is paid to the convergence properties of the LS procedure and we compare it with the simpler Rayleigh-Ritz (RR) procedure in the case when the RR matrix elements are evaluated numerically over the same quadrature mesh as used in the LS procedure. We conclude that although the LS procedure is capable of high accuracy it has no advantages which would justify its sole use in place of the RR procedure. However, it does have some advantages when used in conjunction with RR, in that it gives an estimate of the numerical accuracy of the RR energies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1755-1760 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rates of crystallization of polyethylene fractions have been studied at high undercoolings by differential calorimetry to demonstrate the utility of this technique for fast crystallization analysis. It has been shown that there is continuity in the crystallization kinetics from low to high undercoolings. On the other hand, the influence of molecular weight on the crystallization rates, as the undercooling increases, is very moderate, as would be expected.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 705-710 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent precision measurements of the heats of combustion of atactic and isotactic polystyrene permit an unequivocal calculation of the enthalpy difference in the bulk amorphous forms of the two isomers of this polymer. Contributions to this quantity arise mainly from the differences in nonbonded interactions in the two configurations but may also contain terms relating to higher energy conformations and to intermolecular interactions. The thermochemical and NMR data of specific polymers and of simple molecules are discussed in a comparison with model compound calculations. The thermochemical method has potentially important applications in studying molecular interactions in stereoregular polymers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1627-1637 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fibrous crystals of polyethylene are produced by crystallization from agitated solutions in xylene. If crystallization temperature is maintained between 97°C and 108°C these fibers are free from overgrowth effects and are seen to consist of flat, striated ribbons. This material was treated with fuming nitric acid, and the molecular weight distribution of the degradation product was analyzed by gel permeation chromatography. This distribution was found to consist of a low molecular weight peak and an exceptionally resistant high molecular weight tail over a wide range of degradation times in quantitative agreement with the serrations developed during the nitric acid attack. This is consistent with the fibers possessing a composite folded and extended chain structure. The lateral pulling out of smooth fibrils from the original fibers in the course of certain electron microscope sample preparation methods is consistent with the presence of chain-folded material and might account for the structureless fibrils reported in the literature. Partially successful attempts to obtain the extended chain portion in pure form by selective dissolution are mentioned together with some low-angle x-ray results.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 511-533 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The temperature dependence of x-ray small-angle scattering from fractionated linear polyethylene crystallized from the melt was determined experimentally over a range of temperatures from room temperature to the melting point. It was found in general that only the most intense of the several small-angle peaks exhibited a thermally dependent behavior. Below the crystallization temperature this peak increased in intensity with temperature, at constant peak position. Recrystallization was manifest in a discontinuous shift of the peak. During isothermal crystallization, the peak intensity first increased, then decreased, with time. It is concluded from supplementary electron microscopy and from the behavior of the peak that its position reflects the period of stacking of lamellae and that its intensity is controlled primarily by the thickness of the layer separating lamellae. The reversible peak intensity effect is attributed to an entropydriven growth of the interlamellar layer at the expense of the crystalline lamellae. The intensity effects observed during crystallization are associated with the primary and secondary phases of crystallization. Lamellar surface free energies were computed from melting point observations and were found to increase with molecular weight.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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