HYPERNETTED AND REFERENCE HYPERNETTED CHAIN INTEGRAL-EQUATIONS FOR LENNARD-JONES DIATOMIC FLUIDS WITH QUADRUPOLAR INTERACTIONS

The hypernetted chain and reference hypernetted chain integral equations are solved for quadrupolar two-center Lennard-Jones fluids and the computed fluid structure and thermodynamics are contrasted with computer simulation. A reference bridge function is determined through an empirical modification of Verlet's approximation. The resulting reference hypernetted chain equation leads to good agreement with simulation data. On the contrary, the bare hypernetted chain approximation performs poorly, in particular as far as the equation of state is concerned, which is a well-known drawback of this closure when short ranged repulsive potentials come into play.