Strength and directionality of the C(sp3)H⋯S(sp3) interaction. An ab initio study using the H2S⋯CH4 model complex

Using the MP2 and MP4 methods and extended basis sets, the potential energy surface of the H2S⋯CH4 complex was examined to locate all its minimum energy conformations. Two minima are found, characterized by CH⋯S and SH⋯C intermolecular contacts; at the MP2 level, the basis-set superposition error-corrected interaction energy is −0.42 and −0.84 kcal/mol, respectively, similar to the MP2 values previously found for the CH⋯O and OH⋯C interactions (−0.49 and −0.72 kcal/mol). The anisotropy of the CH⋯S interaction is also studied.