摘要:

The totality of structures, for a limited basis valence-bond calculation on methane and its positive ion, is classified according to their spatial symmetry and spin multiplicity. The structures contributing to the spin optimized and all-singlet coupled forms of the separated-pair model are then enumerated, and a discussion is given of an approach for removing the restrictions inherent in these models. The analysis is also used to classify the configurations in an MO-based CI calculation on methane. Finally, a short discussion is given of the valence state of carbon in methane and its positive ion, allowing for contributions from neutral and all ionic states of carbon.

ISSN:0026-8976    

DOI:10.1080/00268977500101131

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

We discuss the electronic structure of Li2S. In particular it is shown that the changes in ionicity predicted by population analysis on making such systematic changes as varying the apex angle are much greater than one would expect from a consideration of observables like quadrupole moment. The polarization of atomic densities needs to be carefully considered. Density difference maps are presented and discussed.

ISSN:0026-8976    

DOI:10.1080/00268977500101141

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Literature definitions of magnetic multipole moment operators are shown to be at variance, and new definitions are formulated which are consistent with a general multipole interaction hamiltonian and with the radiation field of a dynamic charge distribution. The applicability of traceless multipole moments is examined.

ISSN:0026-8976    

DOI:10.1080/00268977500101151

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Recently Lee and Levesque have extended the Weeks-Chandler-Andersen pure fluid perturbation theory to mixtures and have compared the results to the Leonard-Henderson-Barker mixture theory. The results seem to favour the Leonard-Henderson-Barker theory. This and other previous comparisons of mixture theories have been mostly confined to the study of ‘zero pressure’ thermodynamic properties. In this paper we compare the Lee-Levesque, Leonard-Henderson-Barker and the van der Waals one-fluid theories to high pressure equation of state data for helium-xenon mixtures. This system is modelled by a binary mixture of Lennard-Jones fluids and the hard sphere reference system is characterized by the Grundke-Henderson hard sphere mixture radial distribution function. The Lee-Levesque theory compares favourably with experimental equation of state data up to pressures of 2000 atmospheres. The Leonard-Henderson-Barker and van der Waals one theories are satisfactory. Although the van der Waals one theory yields the poorest results, it does offer the advantage of having the greatest ease of computation.

ISSN:0026-8976    

DOI:10.1080/00268977500101161

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The general theory [1] of bimolecular collision-induced infra-red absorption in linear molecules is applied to the particular cases of dipole, quadrupole, octupole, and hexadecapole-induced dipole absorption. Some of the resulting equations are used to reproduce the profile and intensity of the far infra-red (20–400 cm-1) absorption measured by Bosomworth and Gush

ISSN:0026-8976    

DOI:10.1080/00268977500101171

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Some one-electron molecular properties are calculated for BH3, BH4-, B2H6, B4H4, CH4, C2H2, C2H4, C2H6, and C3H4. The wave functions used are constructed from minimal basis sets of STO's and FSGO's. The results obtained from the latter wave functions show that the good agreement with the STO values of the molecular energy is not always maintained with one-electron properties.

ISSN:0026-8976    

DOI:10.1080/00268977500101181

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The relaxation of the two-proton system longitudinal magnetizationMz(t)is considered theoretically, using the Bloch equations with a diffusion term. The condition <ℋdd> τc≥ 1, <ℋdd> τ ≪ 1 is fulfilled here, where <ℋdd> is the energy of the proton dipole-dipole interaction, τ is the correlation time of molecular diffusion rotation and τ is the correlation time for the proton rotation relative to the molecule. Unlike the ordinary Bloch equations a two-exponential law for the evolution ofMz(t)is obtained for definite values <ℋdd>, τcand τ. The results of the present work may be useful for the consideration of the system having mobile proton groups in viscous media.

ISSN:0026-8976    

DOI:10.1080/00268977500101191

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A Cl2- centre has been trapped in X or γ-irradiated Ca(ClO3)2. 2H2O single crystals at 298 K, when the irradiated crystals were illuminated with ultra-violet light (360 nm). This centre is formed at the expense of ClO2centres in this crystal. This Cl2-centre is trapped at two magnetically inequivalent sites in the crystal lattice and these sites become equivalent when the static magnetic field is parallel or perpendicular to thebaxis. At many orientations this centre reveals ‘super-hyperfine’ interaction with a proton (I= 1/2) of the water of crystallization. The magnetic parameters are close to those observed in alkali chlorides and the E.S.R. spectrum has been fitted to an orthorhombic spin hamiltonian. The principalgvalues aregxx= 2·035,gyy= 2·033 andgzz= 2·000 and those of theAvalues areAxx= 15·0,Ayy= 31·0 andAzz= 109·0 G. The shfs parameters areA‖' = 5·0A⊥' = 1·0 G. The VKcentre trapped in this lattice is exceptionally stable at room temperature.

ISSN:0026-8976    

DOI:10.1080/00268977500101201

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A simple procedure for imposing upper and lower bounds on the dynamical polarizability of a ground-state atom or molecule at frequencies higher than the first transition frequency is described. The method makes use of low frequency refractive index information together with bounds on the first few oscillator strengths. Successive transformations are used to construct a type of multipoint Padé approximant, yielding bounds on the dynamical polarizability which take into account the scatter in the experimental data. The method is applied to krypton.

ISSN:0026-8976    

DOI:10.1080/00268977500101211

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A method is described for constructing analytical potentials for the ground states of stable triatomic species from spectroscopic data. The method leads to potentials which reproduce both the equilibrium and asymptotic properties of the molecule. Application of the method to H2O leads to a potential surface which agrees with known experimental and theoretical data. For example, the predicted reaction coordinate for theC2vinsertion of O(1D) into H2is in good agreement with published calculations.

ISSN:0026-8976    

DOI:10.1080/00268977500101221

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor