Large basis set study of the stability of (H2S)2: the importance of 3d functions in weak interaction of second row molecules

Correlated ab initio calculations on the stability and structure of the weakly bound dimer of H2S have been carried with extended basis sets. One sulfur 3d function is deficient for describing electrical interaction and dispersion. This is partly masked by an exaggeration of permanent moment interaction opposing an undervaluation of dispersion. With three 3d functions, the interaction is fairly stable with respect to further basis enlargement including the addition of 4f functions. The highest level results give an interaction energy of about 500 cm−1and an equilibrium center-of-mass separation distance of 4.08 Å.