摘要:

A numerical iteration algorithm is presented for the computation of pair correlation functions of soft sphere repulsions in the Baxter reformulation of the Percus-Yevick integral equation. The method consists of the determination of accurate initial values and the derivation of a sum recursive rule, which reduces the computational time by a factor of about 40 compared to that of the previous methods.

ISSN:0026-8976    

DOI:10.1080/00268979000100441

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The thermodynamic properties and structure of liquid benzene have been studied by means of the nonspherical perturbation theory due to Fischer after modelling it as a fused sphere body with the six centre Lennard-Jones potential. It is shown that the perturbation theory is capable of predicting the liquid density within a few per cent of that obtained from molecular dynamics simulation. Also, the calculated sound velocity as a function of pressure and temperature is in good agreement with the experimental data. However, the theory is found to be less satisfactory for structure prediction which leads to large errors in the predicted configurational internal energy.

ISSN:0026-8976    

DOI:10.1080/00268979000100451

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The orientation partition function, the associated angle-averaged Mayerf-function, and the effective isotropic potential for a pair of dipoles are expressed in terms of a twice-modified incomplete Struve function of zero order. The partition function is a genus one, order one, type two entire function, with an infinite number of zeros along the imaginary axis. Analytic expressions are derived that characterize it throughout the complex plane. These expressions provide efficient means for computing the partition function, the angle-averaged Mayerf-function, and the effective potential. The partition function's distribution of zeros and classical low-temperature behavior resemble that of the partition function for an Ising dipole pair and for a dipole in an external field, but are strikingly different from that of the Boltzmann factor of the attractive component of the Lennard-Jones effective potential of dipolar thermodynamic perturbation theory.

ISSN:0026-8976    

DOI:10.1080/00268979000100461

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Calculations are presented for the lowest 900 vibrational (J= 0) states of the LiCN floppy system for a two dimensional potential energy surface (rCNfrozen). Most of these states lie well above the barrier separating the two linear isomers of the molecule and the point where the classical dynamics of the system becomes chaotic. Analysis of the wavefunctions of individual states in the high energy region shows that while most have an irregular nodal structure, a significant number of states appear regular—corresponding to solutions of standard, ‘mode localized’ hamiltonians. Motions corresponding in zero-order to Li-CN and Li-NC normal modes as well as free rotor states are identified. The distribution of level spacings is also studied and yields results in good agreement with those obtained by analysing nodal structures.

ISSN:0026-8976    

DOI:10.1080/00268979000100471

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new theory based on the Ornstein-Zernike integral equation and applicable to any hard-body molecular fluid is proposed. The theory approximates the bridge function of the molecular fluid by the hard-sphere bridge function with an angular-dependent hard-sphere diameter. The theory is tested on the homonuclear hard-dumbell system over a wide range of elongations and densities. The predicted compressibility factors are numerically indistinguishable from available computer simulation results and the theory also gives a very good description of the pair distribution function, as represented both by the spherical harmonic expansion coefficients and by the site-site distribution functions.

ISSN:0026-8976    

DOI:10.1080/00268979000100481

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Using self-consistent-field (SCF) and configuration-interaction (CI) methods, the electric field gradientsqin LiH were calculated at both nuclear positions. Two series of basis set studies were performed. In one, increasing numbers ofdfunctions were added to contracted Li (10s5p/5s4p) and H(6s4p/4s3p) basis sets. In the other series,dfunctions were added to uncontracted Li(10s6p) and H(8s5p) basis sets. In all cases, energy-optimized or even-tempered orbital exponents were chosen. Finally,ffunctions were added to the uncontracted 10s6p2d(Li)/8s5p2d(H) basis set. The best values obtained are -0·0385 a.u. forq(Li) and 0·0522 a.u. forq(H). Estimates of rovibrational corrections changeq(7Li) from -0·0385 to -0·0380 a.u. andq(2H) from 0·0522 to 0·0517 a.u. Experimentally,q(2H) is found to be 0·0491 a.u. The calculated value ofq(Li) leads to a quadrupole moment for7Li of -0·0391 b and -0·0396 b after rovibrational correction, close to other recent theoretical predictions and close to a new measured value of -0·0403 b, but differing from another measured value of -0·0385 b.

ISSN:0026-8976    

DOI:10.1080/00268979000100491

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

By means of two-dimensional N.M.R. spectroscopy, the sixteen time-averaged magnetic dipolar couplings between proton spins of partially (non-selectively) deuteratedn-hexane oriented in a liquid crystal are determined. Using multiple-quantum N.M.R. together with simple models of the solute energy in the liquid crystalline environment, the dipole couplings are assigned to specific pairs of protons on the hexane molecule. One of the parameters of the models is the trans-gauche energy difference, for which the value consistent with the N.M.R. observations is about 3·5 kJ mol-1, higher than the usually assumed values of about 2·0 kJ mol-1. The order tensors and conformational probabilities derived from the data and models are presented and the possibility of extending these experiments to larger molecules is discussed briefly.

ISSN:0026-8976    

DOI:10.1080/00268979000100501

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In this paper we discuss the interaction of electric polarization and the flow of heat. We show that in polar fluids, the flow of heat causes a spontaneous alignment of molecules generating an electric polarization. For the system studied the reciprocal effect of electric polarization upon the thermal conductivity appears to be weak.

ISSN:0026-8976    

DOI:10.1080/00268979000100511

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Molecular-dynamics calculations have been carried out for a model of argon physisorbed on the (100) surface of magnesium oxide. The commensurate solid at full monolayer coverage is shown to melt by second-layer promotion. At lower coverages, the system is found to evolve spontaneously to a latticefluid state in which motion of the argon atoms is largely confined to the (10) channels between magnesium sites. Comparison is made with the results of recent experiments and with the predictions of the jump-diffusion model of Chudley and Elliott.

ISSN:0026-8976    

DOI:10.1080/00268979000100521

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Isotropic and anisotropic induced contributions in light scattering from water vapour (418–453 K) along the liquid-vapour coexistence curve are studied. The evaluation of the induced effects takes into account the long range interactions described by the first few terms of the polarizability and multipolar series expansion. In performing the configurational averages at low density, different effective potentials in the literature are used and quantum corrections to the classical pair distribution function are considered. The quantum rotational-allowed spectrum is calculated and used to derive reliable intensities and lineshapes of the depolarized induced contributions. The role of the interference between rotational and translational variables (the cross-term) is discussed. The intensity and lineshape of the isotropic contributions are calculated and the theoretical frequency dependence of the depolarization ratio is compared with the experimental one.

ISSN:0026-8976    

DOI:10.1080/00268979000100531

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor