Intermolecular Potential Function for Hydroxylamine Dimer Interactions from ab initio Calculations

Abstract

Abstract The derivation of an intermolecular potential function for the interaction of two hydroxylamine molecules, based on ab initio SCF-ECP calculations is reported. Ab initio values were compared for selected geometries with those obtained from calculations with much larger basis sets, inluding electron correlation effects by the CEPA method. A total 658 energy values were then fitted to an analytic sum of atom-atom isotropic pair potential functions, whose functional form was given a simple electrostatic interpretation. The major difficulties, arising from the relatively low values of the stabilisation energies of the system and the numerous possibilities to form hydrogen bonds, were overcome by a careful selection of sufficient points on the potential hypersurface, introduction of cut-offs and weight factors. The obtained function was seen to be able to give a good reproduction of the interaction energies and proved suitable in a preliminary MC simulation