摘要:

We report a molecular dynamics computer simulation study of hydrogen chloride in the liquid and dense gas states. The intermolecular pair potential model consists of four cut off, shifted-force atom-atom Lennard-Jones (LJ) interactions, to which are added molecular electric point dipolar and quadrupolar interaction terms. The LJ parameters are fixed using the experimental density and vapour pressure of the coexisting liquid. The simulation is used to predict the internal energy and the self-diffusion coefficient for the liquid, and the internal energy and pressure for the supercritical fluid. Good agreement is obtained with experiment for these properties, and the model gives somewhat better results than those found in a previous study [2] in which the electrostatic forces were omitted. The mean squared torque for the liquid is now somewhat larger rather than smaller than the experimental value. We also calculate the site-site correlation functions and partial structure factors, and find in particular that the addition of the electrostatic forces has a large effect on the HH intermolecular pair correlations. Quantum corrections are calculated for the thermodynamic properties, and are larger than for the case where electrostatic forces are omitted but still constitute a small correction.

ISSN:0026-8976    

DOI:10.1080/00268978000101461

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Single crystal and powder E.S.R. studies of low-spin N,N′-ethylene bis(thioacetylacetoneiminato)Co(II) N,N′-ethylenebis(selenoacetylacetone-iminato)Co(II), and some related compounds, diluted in the corresponding Ni(II) and Zn(II) complexes are reported. The Co(II) complexes and their Ni(II) analogues are all isomorphous. The crystal and molecular structure of N,N′-ethylenebis(thioacetylacetoneiminato)Ni(II) is given.

ISSN:0026-8976    

DOI:10.1080/00268978000101471

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An experiment to measure the two-body collision-induced light scattering spectrum of Ar, CH4, CD4, CF4and SF6is described. Contrary to previous studies, the argon spectral intensity is shown to exceed that of the predictions of the first order dipole-induced-dipole model for the pair polarizability anisotropy. It is demonstrated empirically that this intensity can be accounted for by second-order quantum mechanical effects. The spectral profile is analysed in terms of various modifications to the pair polarizability. The main object of this study is to provide a basis for comparison with the molecular spectra described in paper II of this series.

ISSN:0026-8976    

DOI:10.1080/00268978000101481

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The two-body collision-induced scattering spectra of CH4, CD4, CF4and SF6are presented. They are shown to contain features due to collision-induced rotational Raman scattering (CIRS). The spectra are used to obtain estimates of the magnitude of the molecular polarizabilitiesA(dipole-quadrupole) andE(dipole-octopole). The zeroth moment of the translational CIS spectrum also provides further evidence that the pair polarizability β(r) may be accurately described by the point dipole-induced-dipole (DID) model with small dispersion corrections.

ISSN:0026-8976    

DOI:10.1080/00268978000101491

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A study of an orientational model approach for molecular liquid CSe2is given. With proper selection of the centres structure factor and weighting of parallel and perpendicular orientations, an agreement comparable with the reference interaction site model (RISM) calculations can be obtained, except in the lowQregion. Next, from the experimental molecular structure factor data calculations are made for the centres structure factor, centres radial distribution, centres direct correlation, intermolecular potential energy and, finally, the partial structure factor of Se in CSe2.

ISSN:0026-8976    

DOI:10.1080/00268978000101501

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Numerical results for two recently developed theories of molecular fluids are presented and discussed in the case of the hard dumbell fluid over a range of atomic separations. Results for the complete angular-dependent pair distribution function and its spherical harmonic expansion coefficients are more accurate in the case of the RAM theory. The BLIP function theory is satisfactory only at small atomic separations. A novel reduced form of distribution function is proposed and its general theoretical and computational implications discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000101511

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A monomer-dimer system with excluded volume interactions and weak long range attractive interactions is studied on a two dimensional square lattice. The anisotropic version of the exact series expansion method of Nagle-Temperley has been used to obtain the entropy as a function of densities of horizontal and vertical dimers. Both isotropic and anisotropic long range dispersion interactions are taken into account in an approximation of the mean field type. Numerical analysis of the system yields three types of phase diagrams depending on the ratioR= ωa/ωiof the parameters specifying the strengths of anisotropic ωaand isotropic ωiinteractions. For small values ofR(type I) the nematic-isotropic phase transition is second order while for largerR(type II and III) a tricritical point appears below which the phase transition is first order. IfRis large enough (type III) the vapour pressure curve remains entirely in the nematic stability region. There is no crystallization in this model. Lines of classical points of first order (vapour-liquid) and second order (isotropic-nematic) as well as a line of triple points and a line of tricritical points are shown on a generalized phase diagram which is discussed in detail.

ISSN:0026-8976    

DOI:10.1080/00268978000101521

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A theory of the effect of molecular polarizability on the equilibrium properties of dielectric liquids is developed, and then applied to study molecular dynamics calculations of the field of a dipole in non-polar polarizable fluids. The point of view is adopted that molecular polarizability arises because some intramolecular degrees of freedom give rise to single molecule dipole moment fluctuations. Thus intramolecular internal degrees of freedom are explicitly incorporated into a classical statistical mechanical description of the system. To compare with classical molecular dynamics results these internal degrees of freedom are modelled as Drude oscillators. The agreement with the computer simulation results is quite good. These results suggest that this method is capable of providing accurate and convenient descriptions of the effects of molecular polarizability in a variety of more complicated circumstances.

ISSN:0026-8976    

DOI:10.1080/00268978000101531

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In this paper we obtain the theoretical spectra for each possible mechanism for fluorine exchange inRPF4molecules (R= Cl, CH3). The number of lines and their relative intensities are a characteristic of each isomerization mode. The possibility of discriminating between the isomerization modes is discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000101541

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Some spectroscopic consequences of Johnson's hard sphere structural model for polynuclear transition metal carbonyls are investigated. The fluxional motions of the carbonyl ligands are interpreted as collective surface oscillations and the liquid droplet model in nuclear physics is used to calculate the excitation spectrum of these collective modes. According to this conjecture metal cluster carbonyls should have distinctive spectra in the range 10 cm-1–100 cm-1, this being the energy régime where the Born-Oppenheimer rigid-rotor, small-amplitude vibrator model breaks down and highly excited rigid rotor rotational excitations begin to couple strongly with vibrational excitations so as to produce collective excitations that classically are interpretable as large amplitude concerted motions of the ligands about the metal cluster core.

ISSN:0026-8976    

DOI:10.1080/00268978000101551

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor