AN ACCURATE INTEGRAL-EQUATION FOR MOLECULAR FLUIDS .2. HARD HETERONUCLEAR DIATOMICS

The recently proposed VM integral equation theory and the Percus-Yevick (PY) theory have been studied for the hard heteronuclear diatomic fluid over a wide range of sphere elongations, diameter ratios, and densities. The predictions of the structure and thermodynamics were compared with available computer simulation results and with those obtained from the RAM, RISM, and median perturbation theories. The VM theory yields excellent results for the compressibility factors and the site-site spherical harmonic coefficients of the pair distribution function. The thermodynamic consistency between the virial and compressibility equations was also tested numerically and found to be almost exact. The results of the PY theory are not as accurate but still considerably better than those of the RISM and RAM theories. The median perturbation theory yields good results for the compressibility factors up to moderate densities, but its predictions of the structure are expected to be poor.