摘要:

SCF and CAS SCF calculations have been carried out to determine the quadratic and some of the higher force constants of the methane molecule. The calculated SCF value ofreis 1·08258 Å which is very close to Gray and Robiette's experimental value of 1·0858 (±0·0010) Å. Correlation contributions to most of the quadratic constants are significant and are largely recovered by the CAS SCF calculations. The thirty-three independent quartic symmetry co-ordinate force constants are given explicitly for the first time together with additional, dependent quartic constants and some of them calculated at the SCF level.

ISSN:0026-8976    

DOI:10.1080/00268978700100331

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A simple, yet reliable, expression is suggested to represent the radial-dependent charge-overlap damping functions for the coefficients (Cn) of the second-order induction and dispersion perturbation series expansions for arbitrary evenn, and of the third-order charge-overlap induction damping functions for arbitrary oddn. By using a reduced coordinate of the formx=R/[λ + 2γ(<r2A>1/2+ <r2B>1/2)], where λ = 5·5a0and γ = 1.25, it is shown that the charge-overlap damping functions for the H(1s) … H+second-order induction coefficients can be made consistent with those for the H(1s) … H(1s) second-order dispersion coefficients over a wide range of internuclear distances. Hence, in view of previous work, they are suggested to study other ion-atom interactions. Based on the damped induction energy, reliable analytic fits to the exact numerical Born-Oppenheimer curves for theX2Σg+and 12Σu+states of H+2are presented.

ISSN:0026-8976    

DOI:10.1080/00268978700100341

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Neutron diffraction measurements have been made for CCl4/SnCl4liquid mixtures. The tetrahedral molecules have different sizes but the scattering from the central atom is identical. The results indicate a systematic effect of the anisotropy on the magnitude of the first two diffraction peaks and are in good agreement with the theoretical predictions obtained by solving the RISM integral equation using a hard core model in which the effective diameter of the chlorine atoms was evaluated from the Barker-Henderson criterion. We also discuss the main features of the interlocking arrangement of these molecules as shown in the various pair correlation functions and the possibility of using a two-fluid model for describing the intermolecular structure factor of these mixtures.

ISSN:0026-8976    

DOI:10.1080/00268978700100351

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

E.P.R. of Mn2+in single crystals of Zn(acac)2H2O has been measured and the spin-hamiltonian parametersb02,b22andb04as well as the directions of the principal axes of the fine structure tensor have been determined. Application of the superposition model (SPM) showed remarkably good agreement in the orientations of these principal axes with the results of one crystal structure refinement while large discrepancies were observed for the other one. The large value ofb2cannot be rationalized by the SPM with the normal intrinsic zero-field splitting parameterb2for oxygen as ligand in contrast to the behaviour of Mn2+in Mg(acac)2·2H2O with a much smaller value ofb02. Evidently the nonplanarity of the acetylacetonate groups and the Mn2+in the Zn compound causes interaction with the conjugated π-electron system of these ligands. Thus systems with electron delocalization may lead to a breakdown of the SPM.

ISSN:0026-8976    

DOI:10.1080/00268978700100361

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A DV-Xα molecular-orbital calculation was carried out on [Ce(OH2)9]3+. The charge donation of coordinated water molecules results in a net charge of +0·354 on the central tervalent metal ion and an appreciable polarization in the coordinated waters. The coordination bond of the vertex waters is stronger than that of the equatorials. The observed transition moments and energies of the 5d← 4fexcitations as well as the observed ligand-field splitting of2D(5d1) multiplet in theD3hligand field of [Ce(OH2)9]3+were reasonably reproduced by use of the transition-state approximation on the base of DV-Xα molecular-orbital calculation. The model also predicts a contraction of 4forbital while an expansion of 5dorbital in the cluster.

ISSN:0026-8976    

DOI:10.1080/00268978700100371

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Phase transitions at fluid interfaces and in fluids confined in pores have been investigated by means of a density functional approach that treats attractive forces between fluid molecules in mean-field approximation and models repulsive forces by hard-spheres. Two types of approximation were employed for the hard-sphere free energy functional: (a) the well-known local density approximation (LDA) that omits short-ranged correlations and (b) a non-local smoothed density approximation (SDA) that includes such correlations and therefore accounts for the oscillations of the density profile near walls. Three different kinds of phase transition were considered: (i)wetting transition. The transition from partial to complete wetting at a single adsorbing wall is shifted to lower temperatures and tends to become first-order when the more-realistic SDA is employed. Comparison of the results suggests that the LDA overestimates the contact angle γ in a partial wetting situation. (ii)capillary evaporationof a fluid confined between two parallel hard walls. This transition, from dense ‘liquid’ to dilute ‘gas’, occurs in a supersaturated fluid (p>psat). The lines of capillary coexistence calculated in the LDA and SDA are rather close, suggesting that non-local effects are not especially important in this case. (iii)capillary condensationof fluids confined between two adsorbing walls or in a single cylindrical pore. For a partial wetting situation the condensation pressuresp(<psat) obtained from the SDA are in remarkably good agreement with the macroscopic Laplace (or Kelvin) prediction for wall separationsHor pore radiiRc≳ 5σ; σ is a molecular diameter. While, because of different packing, the density profiles of the fluid differ considerably between slits and cylinders this has little effect on the coexistence line untilHorRc∼ σ. In contrast to the LDA the SDA describes two-dimensional-like liquid-gas coexistence for very narrow pores (H< σ) and temperatures below the two-dimensional critical temperature and this has ramifications for the existence of capillary critical points.

ISSN:0026-8976    

DOI:10.1080/00268978700100381

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Hartree-Fock total and orbital energies, multipole moments and electric field gradients are reported for the title molecules (plus H2and HeH+) at the experimental bond distance. The total energies are at most a few millihartree below previous STO ones. The orbital energies of LiF deviate up to 0·01 au. The interaction energies of HeLi+(R= 3·5 au) and HeNe (R= 5·25 au) are also calculated. The deuteron field gradientqDfor CH+(and C6D6) is discussed. A common trend forqD, ωeandRealong the series OH-, HF and NeH+is pointed out.

ISSN:0026-8976    

DOI:10.1080/00268978700100391

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Raman isotropicv1band of methane has been studied along numerous isochoric lines, in a density range 0·2ρc< ρ < 2·5ρc, and over a wide range of temperature 2 . 10-3< (T-Tc)/Tc< 5 . 10-1. A critical density broadening is observed even very far from the critical temperature. This effect is related in a large measure to an enhancement of the frequency modulation correlation time, an order of magnitude of which can be obtained from the band profile.

ISSN:0026-8976    

DOI:10.1080/00268978700100401

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We present the solution of the site-site Ornstein-Zernike equation (SSOZ) for polar hard dumbbell fluids with site-site mean spherical-like (MSA) and hypernetted chain-like (HNC) closures. Numerical solution of this matrix equation is performed using Gillan's method with a renormalization to remove divergences arising from the long-range potentials. The results are compared with Monte Carlo results for pure fluids, and the agreement is good. We consider polar/nonpolar hard dumbbell mixtures where both components have the same elongation and study the change of liquid structure and internal energy with composition.

ISSN:0026-8976    

DOI:10.1080/00268978700100411

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An exact analytical formula for the coefficients damping each individual multipole in the second-order induction for H+2is presented and the first three damping coefficients explicitly evaluated in closed form. Numerical calculation shows that the dampedR-nseries expansion of the induction energy always converges, the first four terms in the expansion accounting for no less than 97 per cent of the exact value over the whole range of internuclear separations.

ISSN:0026-8976    

DOI:10.1080/00268978700100421

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor