On the role of the electron density difference in the interpretation of molecular properties

In this report we use the electron density difference function, δη(r), to present an interesting and useful interpretation of several molecular properties. For example, all of the electric multipole moments of a molecule may be written as Mαβ⋯γmolecule=Mαβ⋯γatoms+Mαβ⋯γcr where Mαβ⋯γatoms is the sum of the moments of the non-interacting atoms and Mαβ⋯γcr depends on δη(r) and is the contribution to Mαβ⋯γmolecule due to charge redistribution upon molecule formation. This interpretation has implications for attempts to represent the multipole moments of an in situ charge distribution by an array of algebraic point charges.