A model for the study of the structure of hard molecular fluids

A model previously introduced to study the structure and thermodynamics of fluids of anisotropic molecules with orientations restricted to certain discrete directions is generalized and used to study normal molecular fluids in which the molecules can rotate freely. The basis is an ansatz for the direct correlation function which depends on the geometry of two molecules. The method leads to the Percus-Yevick solution for hard spheres and to Onsager's solution in the limit of long needles. In this paper it is applied to fluids comprising hard spherocylinders and to fluids of hard ellipsoids.