QUANTUM AND THREE-BODY EFFECTS ON THE SIMULATED IR SPECTRA OF $SF_{6}-(RARE GAS)_{n}$ CLUSTERS

Abstract

A model developed by Eichenauer and Le Roy predicts the shift of the $v_{3}$ band of $SF_{6}$ perturbed by neighbouring atoms in a cluster, as a function of the number of perturbers and their relative $positions.^{1}$ When combined with Monte Carlo or molecular dynamics simulations of the cluster dynamics, it has shown that the IR spectra of these species should provide an incisive means of identifying cluster isomers and their dynamical state (liquid-like vs. solid-like).$^{2}$ However, all applications published to date have been based on the use of classical mechanical simulations for the cluster dynamics and an additive two-body model for the potential energy governing that behaviour. This paper examines the effect on such predicted spectra of: (i) including the Axilrod-Teller-Muto three-body terms in the potential energy surface, and (ii) taking account of quantal effects on the cluster dynamics by using quantum Monte Carlo methods to perform the appropriate canonical averaging which yields the predicted spectra.