Partitioning the electrostatic interaction energy between two charge distributions

Abstract

Treating the interaction between two charge distributions as a joint venture, we explore here the possibility of quantifying the extent of participation of each charge distribution. By introducing the concept of reduced charge analogous to reduced mass, we show that the interaction energy expression between two charges separates into a sum of two terms, one for each charge. This partitioning, in addition to facilitating a graphical representation of atom-based interaction energy components on complementary surfaces involved in a binding reaction, provides additional insights into the mechanism of interaction and binding. We further introduce the idea of representing molecular electrostatic potentials in the interaction view, i.e. potentials at each atom site of charge distribution I due to charge distribution II and vice versa and demonstrate the graphical equivalence of the potentials thus computed with the energy partitioning proposed here. The method is illustrated with applications to a few test cases and binding reactions of small molecules in vacuum and complexation of biomolecules in aqueous medium.