Computer simulations of polyatomic molecules. II - Molecular dynamics studies of diatomic liquids with atom-atom and quadrupole-quadrupole potentials

摘要: The molecular dynamics method has been used to study a model system of 256 homonuclear diatomic molecules governed by intermolecular potentials the form U = UAA + Z7QQ, where is an atom-atom potential and C/QQ quadrupole-quadrupole potential. For both full Lennard-Jones repulsive part only have used, C7QQ with reduced quadrupole moments, Q* $/(e L* L/cr (bond length/atom diameter) between 0.33 0.63 studied, at temperatures * =kT/e from 0.98 3.48 densities p* pal 0.522 1.043 (where ae diameter sphere having volume equal that diatomic). Detailed orientational structure in liquid examined calculating as many 22 terms spherical harmonic expansion angle dependent pair distribution function. At short distances these systems exhibit high degree angular correlation, which increases increasing elongation density. Pair correlation functions calculated models are virtually identical, other parameters being equal, similar those for hard diatomics, indicating radial determined mainly short-range forces. addition moderately strong term produces dramatic changes significant thermodynamic properties. A found give correct qualitative features factor bromine.