COMPUTATION OF GENERAL MULTIPOLE MOMENT EXPANSIONS FOR N ATOMS BY MAPLE

A program written in the MAPLE symbolic computational language was wri tten to compute analytic and numerical expressions for the long-range multipole moment expansion of the electrostatic (Coulombic) perturbati on operator for a system of N atoms in arbitrary orientations in space . These expressions are written in terms of the multipole moment opera tors on individual interacting atoms. The program was tested on a syst em consisting of a ground-state hydrogen atom interacting with two pro tons in three different configurations, and the results were found to be in agreement with manual calculations. This approach can produce, w ith relative ease, the long-range multipole expansion for systems with large numbers of interacting atoms or ions. (C) 1997 John Wiley & Son s, Inc.