Computer simulations of polyatomic molecules. III. Monte Carlo studies of heteronuclear and homonuclear hard diatomics

Abstract

Monte Carlo computer simulations have been carried out for fluid systems of 256 and 500 heteronuclear and homonuclear hard diatomic molecules, each consisting of fused hard spheres of diameters σ_AA and σ_BB with centers separated by distance L. Nineteen different models have been studied, with elongations L*=L/σ_AA in the range 0.05⩽L*⩽0.75, and diameter ratios γ=σ_BB/σ_AA in the range 0.5⩽γ⩽1.0. The atom–atom distribution functions g_αβ(r), for these models are described in detail, and the discontinuities in their first derivatives at distances σ_αβ+L, predicted by cluster expansion theory, are shown to have a simple explanation in molecular geometry. Pressures have been calculated from a virial‐like equation and used to examine trends in pressure with changes in molecular geometry. Structure factors S (K) and direct correlation functions c (r) have been calculated by Fourier transform of the g_αβ(r), and the dependence of these functions on molecular geometry has been examined.