摘要:

This paper describes the extension of the recently developed Reverse Monte Carlo technique to the problem of molecular liquids. The technique has been applied to available neutron and X-ray diffraction data on the liquid halogens and on liquid nitrogen. The molecular centres structure factors and pair correlation functions have been calculated and the molecular correlation functiong(r, θ1, θ2, φ) has been expanded as a sum of spherical harmonics. The results show that orientational correlations are largely confined to the nearest neighbour coordination shell. Although these correlations are partly due to geometric factors there is also an increased tendency for the molecules in the heavier halogens to be aligned end to end.

ISSN:0026-8976    

DOI:10.1080/00268979000100111

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pure rotational transitions in the[Xtilde]2Π3/2state of the NCO radical have been measured by far infrared laser magnetic resonance (L.M.R.) spectroscopy. Analysis of the Zeeman patterns leads to new determinations of the centrifugal distortion parameters,DandH, the lambda doubling parameterqand theg-factorsgrandg′L.

ISSN:0026-8976    

DOI:10.1080/00268979000100121

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We study two systems of hard biaxial molecules: hard spheroplatelets and hard ellipsoids, using the liquid-crystalline version of the smoothed density approximation (SDA). The first system is studied for all elongations of the spheroplateletc, whereas the second only forc⩽ 7. For both systems, we locate the line of Landau bicritical points at which a direct transition from the isotropic phase to the biaxial phase occurs. We find that the density of the isotropic phase at the Landau bicritical point is always higher than that at the isotropic-nematic transition in the limit of uniaxial molecules and the difference ranges from 10 to 30 per cent. For hard ellipsoids, we obtain a similar scaling behaviour at the Landau bicritical point as for spheroplatelets, i.e.b∼c1/2, wherebdenotes the breadth of the ellipsoid.

ISSN:0026-8976    

DOI:10.1080/00268979000100131

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We demonstrate on a simple model of an ion-dipole mixture that the convergence of a Monte Carlo simulation at low ionic concentration may be quite slow. For a one molar concentration 105trial moves per particle are needed for a 864 particle system to obtain a precise estimate of both the ion-dipole and ion-ion energies and the static pair correlation functions. Our results show that recently published Monte Carlo results (1989,Molec. Phys.,66,299) on a similar system are far from being converged and question the conclusion drawn in this publication on the failure of the reference hypernetted chain equation.

ISSN:0026-8976    

DOI:10.1080/00268979000100141

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor