Theoretical study of intermolecular potential energy surface for HCl dimer: Example of nonspherical atom–atom exchange repulsion interaction

The intermolecular part of the potential energy surface for the HCl dimer has been studied with ab initio quantum chemical methods. An intermolecular potential, based on quantum chemical calculations has been constructed. The interaction energy consists of electrostatic, induction, and dispersion terms calculated from the monomer properties of the interacting molecules and an exchange repulsion term. The latter term was parameterized from the results of the quantum chemical calculations and estimates of the electrostatic and induction energies. It was found necessary to use nonspherical atom–atom exchange repulsion interaction parameters, and the parameters describing the deviation from spherical behavior could be obtained from the expectation values of r² for the electrons assigned to an atom. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1816–1825, 1998