Statistical Mechanical Theory of Rod-Like Molecular Fluids with Kihara-Type Interactions. I. Molecular Distribution Functions

Abstract

Abstract A simplified integral equation for the pair distribution function of linear molecules interacting via a potential depending only on the shortest distance between molecular cores, is written down. The theory is developed starting from the Ornstein-Zernike equation and the Percus-Yevick closure relation, both for non-spherical particles. Two basic assumptions are made. Firstly the molecular pair distribution function is supposed to depend explicitly on the shortest distance but not on molecular orientations; secondly the direct correlation function inside the integral in the Ornstein-Zernike equation is approximated by some average value conveniently defined. The new integral equation is numerically solved for CO2 and N2 assuming a Kihara potential. The main features of the distribution function, particularly its behaviour with temperature and density, are also investigated. The results obtained seem to agree well with a very probable structural model for liquid CO2 and a reasonable model for N2.