Intermolecular interaction energies by topologically partitioned electric properties. 1. Electrostatic and induction energies in one-centre and multicentre multipole expansions

Abstract

Certain difficulties with the usual one-centre multipole expansion of long-range intermolecular interaction energies can be circumvented by multicentre multipole expansions using several expansion sites in each molecule, such as, e.g., the nuclear positions. Based on the topological partitioning of the molecular volume provided by Bader's ‘atoms in molecules’ theory, a method has been developed for calculating the required atomic multipole moments and polarizabilities. The performance of these topologically partitioned electric properties is examined for the calculation of multipole expanded first-order electrostatic and second-order induction energies by comparing their convergence behaviour with that of the corresponding one-centre expansions. The homomolecular dimers of the water, carbon monoxide, cyanogen, and urea molecules serve asexamples.The results show thatdistributedelectricproperties calculated within the topological partitioning scheme indeed solve the ‘shape’ convergence problem, which arises in the calculation of interaction energies of large non-spherical molecules via multipole expansions.