ISSN:0026-8976    

DOI:10.1080/00268978700102011

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The structure of binary fluid mixtures has been studied using the Ornstein-Zernike equation in the Percus-Yevick (P-Y) approximation. Through the Kirkwood-Buff formalism, the mixture spinodal curves and critical loci have been determined. Results for systems with various interaction parameters are presented to demonstrate the influence of differences in molecular size and attractive interactions upon the critical locus. The predictions of the P-Y theory are compared with those of the van der Waal's one-fluid (vdW-1) theory as well as recent estimates from Monte Carlo computer simulations. Quite good agreement with the computer simulation results for the critical locus is obtained. The P-Y and vdW-1 theories predict the same qualitative behaviour for each of the systems studied.

ISSN:0026-8976    

DOI:10.1080/00268978700102021

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In consequence of recent advances made mainly inab initiomethods, relatively accurate anharmonic force fields are beginning to be available for an increasing number of molecules. This makes the calculation of anharmonic vibrational averaging effects on various molecular properties practical. In the present paper this calculation is discussed in detail, pointing out the simplifications which result when the effects of anharmonicity are specified by the conversion between the equilibrium and average geometries of the molecule. The different contributions to the vibrational averages of the internal coordinates of the molecules HCN, C2H2, CH4, C6H6and NH3are reported, considering their sensitivity to the details of the force fields used in the calculation. By combining the results with the experimental structures of these molecules their equilibrium or average geometries are derived.

ISSN:0026-8976    

DOI:10.1080/00268978700102031

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A variational procedure using numerical wavefunctions is presented for the determination of the vibration-rotation levels of triatomic molecules. The procedure is applicable to both linear and bent molecules, which is demonstrated by application to the systems H2O, OCS, and CH+2.

ISSN:0026-8976    

DOI:10.1080/00268978700102041

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The relative stability of various crystal packings of a homonuclear diatomic molecule is investigated as a function of the anisotropy in the intermolecular atom-atom potential. It is shown that different crystal structures can be predicted if the electrostatic interaction arises from a quadrupolar rather than dipolar distortion of the atoms from spherical, for the same total quadrupole moment, and that the corresponding anisotropy in the repulsion-dispersion potential also plays a significant role in determining the minimum energy crystal structure. These results are used to account for the diverse experimental crystal structures of the homonuclear diatomics in terms of their valence electron distribution, and provide a starting point for the development of realistic intermolecular model potentials.

ISSN:0026-8976    

DOI:10.1080/00268978700102051

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A statistical mechanical model of chemically reactive fluids in an inert solvent exhibiting liquid-gas criticality is studied using analytically solvable integral equation approximations. The model consists of a mixture of three molecular species (A, BandC), two of which (the solutesAandB) can undergo reaction and one of which (the solventC) is inert. Particular interest centres on the results for the chemical equilibrium obtained near the mixture critical point of the solution.

ISSN:0026-8976    

DOI:10.1080/00268978700102061

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Griffin-Hill-Wheeler-Hartree-Fock equations are applied to generate universal gaussian and Slater-type basis sets for the title atoms. The results for the energies compare competitively with atom-optimized calculations at a very low computational cost.

ISSN:0026-8976    

DOI:10.1080/00268978700102071

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A solitonic regime has been found in a γ-irradiated single crystal of the malonic acid-urea 1 : 1 adduct. The study has been performed on the α-protons of the radicals by taking advantage of the high resolution of ENDOR spectroscopy and by a careful reproduction of the lineshapes. A solitonic density corresponding to 40 per cent of the radicals present in the single crystal has been obtained. The soliton can be equally ascribed to an incommensurate crystallographic phase or to a solitonic wave excited and sustained by a double-well hydrogen bond present in the crystal. The 1 : 1 adduct seems to have a high electrical conductivity when measured in the crystallographic plane containing the adduct itself.

ISSN:0026-8976    

DOI:10.1080/00268978700102081

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The hyperfine coupling constant for the nitrogen atom is evaluated by large-scale MRD-CI calculations. A detailed analysis of the charge density at the nucleus and the spin polarization in the 1sand 2sshell as a function of various technical parameters is undertaken. Various (s, p) AO basis sets and the influence of correlation orbitals is investigated as well as selection threshold and other properties in CI calculations. The best value, obtained for the isotropic hyperfine coupling constant in ans, p, dbasis, based on theoretical judgment of ‘best’ quantities, is 9·9 MHz compared to 10·4509 MHz.

ISSN:0026-8976    

DOI:10.1080/00268978700102091

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The palladium-ethylene interaction is studied through pseudopotential SCF and CI calculations. It is concluded that the1A1ground state of the Pd-C2H4molecule is bound (47 kJ/mol) relative to Pd(4d105s0) + C2H4(1Ag). The ethylene geometry is slightly perturbed with a C-C distance of 1·4 Å and the HCH bonds bent 16° out of the ethylene plane. A comparison with experimental results for the Pd-C2H4system, as well as with other theoretical studies including electron correlation effects for transition metal-ethylene systems, is presented.

ISSN:0026-8976    

DOI:10.1080/00268978700102101

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor