Cross Second Virial Coefficients of the H2O-H2S and H2O-SO2 Systems from First Principles

The cross second virial coefficients B-12 for the interactions of water (H2O) with hydrogen sulfide (H2S) and of water with sulfur dioxide (SO2) were determined at temperatures from 200 to 2000 K employing new intermolecular potential energy surfaces (PESs) for the H2O-H2S and H2O-SO2 molecule pairs. The PESs were fitted to interaction energies calculated for more than 50 000 configurations of each molecule pair using quantum-chemical ab initio methods up to coupled cluster with single, double, and perturbative triple excitations [CCSD(T)] with consideration of relativistic effects. The B-12 values were extracted from the PESs both classically and semiclassically using the Mayer-sampling Monte Carlo scheme. In addition, accurate correlations of the final B-12 values were used to derive the dilute gas cross isothermal Joule-Thomson coefficients, phi(12) = B-12 - T(dB(12)/dT). For both investigated systems, Wormald provided the only experimentally based B-12 and phi(12) values available in the literature. While his B-12 values, which he obtained from the phi(12) data with the aid of model potentials, are not in satisfying agreement with the present B-12 values, his phi(12) data, after a reanalysis using more accurate pure-component phi values, agree very well with the calculated phi(12) values of this work.