Intermolecular interaction energies of 20 orientations of crown-shaped S-8 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 epsilon = 0.398 kcal mol(-1), A = 1.294 angstrom(-1) and R* = 4.007 angstrom. 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. (C) 2008 Elsevier B.V. All rights reserved.