Theoretical study of three-body nonadditive interactions for the H2S-(H2O)2 system

An ab initio SCF MO study of the hydrogen-bonded system formed by an H₂S molecule interacting with two water molecules is presented. The nonadditive contributions to the interaction energies are obtained using the 4-31G basis sets which tend to overestimate the dipole moments of the H₂S and H₂O molecules. Thus possibly too large interactions, including upper-limit values for the nonadditive three-body contributions, were obtained. The nonadditive corrections were found to be comparable in magnitude to the cases of other first-row hydride trimers. On this basis one can infer that they probably do not affect the proton and deuterium exchange in hydrated H₂S (as occurs in the G-S heavy water enrichment process) and that they do not play an important role in the formation of clathrates involving hydrogen sulphide.