Potential energy surface of S8 dimer

Intermolecular interaction energies of 20 orientations of crown-shaped S8 dimers were calculated at the MP2/aug(df)-6-311G* level with ab initio calculations. The strongest attraction of the dimers studied was 9.924 kcal mol−1, for the face to face orientation. The potential energy surface was represented as a parameterised sum of atomic pair potentials. The sulphur atomic pair parameters of the Morse potential function were ε = 0.398 kcal mol−1, A = 1.294 Å−1 and R∗ = 4.007 Å. A comparison to the solid state structures of S8 showed that the best gas phase dimer orientation is close to the closest packing of S8 dimers in crystalline state.