Perturbation theory for the Lennardhyphen;Jones diatomic fluid. I. Sitehyphen;centered spherical harmonic coefficients

摘要

The RAM perturbation theory is tested via calculations of spherical harmonic coefficientsGklmof the sitendash;site pair correlation functionG(12) for Lennardhyphen;Jones diatomic fluids at a range of elongations and state conditions. The accuracy ranges from good to excellent, depending upon the particular form of implementation of the theory. Although not a necessary prerequisite, the accuracy of the theory may be improved when exact values of the average sitendash;site pair correlation function are used as input quantities in the calculations. This permits comparison with a set of alternative theories which require such input information, and which are based on the sitehyphen;superposition approximation (SSA). In addition to the intrinsic advantage of possessing the ability of compute the fullG(12), the accuracy of the RAM results appears always to be equal to or better than that of the SSA theories.