Pairwise-additive analytic potential for the Ar–CH3CH3 van der Waals complex

We present an analysis of the intermolecular potential for the argon–ethane system. The potential energy surface has been calculated using coupled-cluster theory at the CCSD(T) level extrapolated to the complete basis set limit and has been used to develop a pairwise-additive analytic potential. We have identified two potential minima for each conformation, corresponding to axial and equatorial positions for the argon atom. We present calculated equilibrium geometries and selected spectroscopic constants for these clusters, predicting a reduction of 27 cm−1 in the torsional barrier height of ethane on complexation at the equatorial position, with no change for complexation at the axial position.