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

Abstract

The cross second virial coefficients B₁₂ 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 B₁₂ values were extracted from the PESs both classically and semiclassically using the Mayer-sampling Monte Carlo scheme. In addition, accurate correlations of the final B₁₂ values were used to derive the dilute gas cross isothermal Joule-Thomson coefficients, ϕ₁₂ = B₁₂ - T(dB₁₂/dT). For both investigated systems, Wormald provided the only experimentally based B₁₂ and ϕ₁₂ values available in the literature. While his B₁₂ values, which he obtained from the ϕ₁₂ data with the aid of model potentials, are not in satisfying agreement with the present B₁₂ values, his ϕ₁₂ data, after a reanalysis using more accurate pure-component ϕ values, agree very well with the calculated ϕ₁₂ values of this work.