摘要:

Ab initiocalculations of some diatomic molecules are carried out at large internuclear distance. The spin and space symmetry unrestricted Hartree-Fock method is employed to obtain proper dissociation products. The choice of the starting orbitals, overcoming of convergence difficulties and the influence of spin projection are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000102921

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Potential curves for diatomic hydrides of second row atoms have been calculated using theab initioUMP2 method. A small gaussian basis set is proposed in which the curves are found to be in good agreement with experiment. Reasons for systematic deviations in the range of intermediate internuclear distances are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000102931

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The Foldy-Wouthuysen hamiltonian is used to obtain the energies of various states of the hydrogen-like atom. For the 1sand 2sstates to ordermc2α6and for the 2pstates to ordermc2α8divergent contributions to the energy arise, but it is shown that provided these divergences are handled properly they cancel one another and the correct finite result is obtained. An attempt to carry the calculations to higher orders using delta function recipes fails, but it proves possible to evaluate themc2α8energy contribution for the 1sstate using a different method.

ISSN:0026-8976    

DOI:10.1080/00268978000102941

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Self consistent field-Xα molecular orbital calculations have been performed for Si2and Cl2using both the scattered-wave (SW) and LCAO discrete-variational (DV) versions of the method. For Si2an SW calculation includingfpartial waves yields orbital densities in good agreement with those from methods which do not involve the muffin-tin approximation for the potential. The present results afford a further comparison relevant to the recent discussion (see, M. Schlüteret al.[9]) of the relative accuracy of various pseudocharge densities compared with real charge densities. The deformation density from the Xα-SW calculation is in good agreement with that from the DV-Xα method and also with that from the linear muffin tin orbital method (J. Harris and R. O. Jones [8]). Differences between the valence electron distribution which is usually discussed in connection with pseudopotential schemes, and the density distribution including the 2sand 2pcore electrons are delineated. For Cl2, the Xα-SW deformation density shows positive lobes along lines through the atoms perpendicular to the bond axis, is negative for most of the area between the atoms and also shows negative lobes behind the atoms. This deformation map is in good qualitative agreement with the DV-Xα map and also with recentab initioresults with the exception of a small region at the centre of the bond in which the DV-Xα andab initioresults show an excess of electrons compared with the promolecule whereas the Xα-SW results show a deficiency. Comparisons with X-ray results on solid chlorine are inconclusive so that experimental electron scattering data on gas phase chlorine will be required to resolve this difference.

ISSN:0026-8976    

DOI:10.1080/00268978000102951

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The He(I) and He(II) photoelectron spectra of Fe(CO)2(NO)2are reported and suggest a different assignment of the low energy region of the spectrum from that given by previous SCF calculations. Extended basis set calculations are described which include limited correlation effects in the ground and ionic states. These calculations show that it is the greater correlation energy associated with the Fe-NO π bonding molecular orbitals, compared to the iron 3dorbitals, which is responsible for the incorrect ordering of the ionic states given by SCF calculations.

ISSN:0026-8976    

DOI:10.1080/00268978000102961

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A theory of the velocity autocorrelation function in terms of the longitudinal and transverse momentum current densities has recently been derived by Gaskell and Miller. It has been strikingly successful in some liquid metal-like systems, and we report its application here to a rigid sphere fluid, which perhaps provides a more searching test of its treatment of binary encounters.

ISSN:0026-8976    

DOI:10.1080/00268978000102971

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A microscopic theory of depolarized Rayleigh-Brillouin spectra for viscoelastic liquids is developed. The theory takes into account the oscillation as well as relaxation of shear modes which couple to the polarizability density in a rotationally isotropic system. The experimental results of liquid and supercooled liquid salol have been analysed using the present theoretical result. Not only the detailed lineshape of the spectra at all temperatures can be interpreted consistently using one equation, the temperature dependence of the intensity ratio of the central component to the shifted shear mode side bands can also be accounted for. It is expected that this theory is applicable to the interpretation of depolarized Rayleigh spectra of supercooled liquids or glasses consisting of optically anisotropic molecules.

ISSN:0026-8976    

DOI:10.1080/00268978000102981

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Potential energy functions have been derived for the ground state surfaces of LiFH and H2F by fittingab initiodata. Standard deviations of ∼7 kJ mol-1are obtained for both surfaces. For LiFH it is predicted that a stable linear hydrogen bonded complex exists with energy 11·5 kJ mol-1below the Li + HF dissociation limit. These functions are valid for all configuration space. For H2F the surface is two-valued with a line of intersections in the space ofC2vstructures. The correct saddle point behaviour for both the symmetric and asymmetric exchange reactions have been reproduced, a feature not previously reproduced by LEPS functions.

ISSN:0026-8976    

DOI:10.1080/00268978000102991

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

From a many-body theory of optical scattering we derive a relation for the collective behaviour of incoherently scattered light emerging from a molecular fluid. The relation involves a surface integral and has precisely the mathematical form of the Ewald-Oseen extinction theorem; it is exact in the sense of that theorem. We prove from the relation that scattered radiation is refracted and reflected at the surface of the scattering medium according to rules inferred from macroscopic optics. The relation provides a construction of contributions to the scattering with any number of internal reflections; it applies also to scattering restricted by stops. Explicit expressions for the surface dependent scattering in terms of a Fresnel transmissivity correct a previously reported theory of bulk scattering.

ISSN:0026-8976    

DOI:10.1080/00268978000103001

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Diffusional mechanisms of relaxation properties are considered in the case where the individual jump frequency is comparable with that of the external-force oscillation. All probable trajectories of a kinetic element are taken into account and a kinetic equation for a finite time interval is obtained. The problem is solved for infinite one-dimensional and three-dimensional media. The resulting diffusional differential equations contain infinite series of higher-order derivatives with respect to the time and space coordinates. A Fourier transformation of the solution yields the frequency-dependence of the wave vector in a simple form.

ISSN:0026-8976    

DOI:10.1080/00268978000103011

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor