Dynamic global potentials and second virial coefficients from trajectory calculations

We report on a novel method of verifying the validity of intermolecular potentials. By using trajectory calculations with an ab initio pairwise potential or an assumed Lennard-Jones pairwise potential, we calculate the intermolecular dynamic global potential which can be used to calculate experimentally obtained quantities such as a second virial coefficient. The agreement between calculated and experimental quantities is a measure of the quality of the intermolecular potential that is used in such calculations. The method is demonstrated for benzene-Ar collisions. An ab initio and a Lennard-Jones pairwise potentials ate used, and calculations of the dynamic global potential and the second virial coefficient were performed at 300, 700, 1500, and 2820 K. It is found that the dynamic global potential is a function of the temperature, and explanations which rake into consideration the anisotropic potential of the benzene molecule and the effects of the vibrational, rotational, and translational energies on the dynamic global potential are provided. The method applies to neat gases as well as to binary gas mixtures.