Direct Use of the Diatomics-in-Molecules Method in Large Systems and in Dynamical Calculations

Abstract

The rapid calculation of potential energy surfaces is a pre-requisite for dynamical calculations as well as for the investigation of systems having a large number of degrees-of-freedom. Such calculations can be effected readily by the method of diatomics-in-molecules (DIM), which is capable of treating ground and excited states on a nearly equal footing. The development of a new computer program enabling application of the method to an arbitrary molecule is described. The utility of the new program is illustrated by reference to three physical systems with widely differing requirements: (1) electronic structure calculations of ionised rare-gas clusters (many degrees-of-freedom); (2) The interaction of excited and ground state alkali atoms in the neighbourhood of a metal surface (excited states, large number of degrees-of-freedom); and (3) the reaction dynamics of O(¹D) + H₂ → OH(X²Π) + H (excited states, trajectory calculations). The DIM program is so constructed as to be directly usable in a trajectory program.