2ND VIRIAL-COEFFICIENTS FOR ATOM-MOLECULE COMPLEXES FROM AB-INITIO SAPT POTENTIALS

Ab initio potentials, calculated by symmetry-adapted perturbation theo ry, are applied to compute second virial coefficients (including first order quantum corrections) for He-CO, Ne-CO, Ar-H-2, He-C2H2, and Ar- CH4 mixtures over a wide range of temperatures. The experimental metho ds are briefly outlined and the errors in the procedure to obtain mixe d virial coefficients from the experimental data are discussed. Very g ood agreement with the majority of the available experimental data is observed for all systems except Ar-CH4 where calculated virial coeffic ients are slightly too high in comparison with measured data. Possible reasons for discrepancies between theory and experiment at very low t emperatures are discussed.