H ··· H model potential for exchange-repulsion energy of methane dimer

The procedure previously proposed for the parameterization of the exchange]repulsion energy using probe atom calculations is applied here to the study of the methane dimer and refined to give a very accurate anisotropic model potential in terms of atomic parameters. The most accurate model uses sites on C and H atoms and requires 12 parameters, but a description using just four isotropic sites shifted inward from the H atoms by 15% of the bond length is almost as accurate and is very simple in form. Q 1998 John Wiley & Sons, Inc. J Comput Chem 19: 847]857, 1998