Ground-state charge transfer and electronegativity equalization

Abstract

The intuitive picture suggesting that ground-state charge transfer is associated with differences in ionization potentials of donor and acceptor molecules is studied in terms of an MC-SCF scheme. This leads to the definition of effective molecular electronegativities and to the formulation of a principle of electronegativity equalization as the condition for charge transfer in the ground state at distances where binding effects proper are negligible. Even in that extreme case charge transfer is found to be directional, because of its dependence on electronegativity differences and on an effective intermolecular Coulomb integral. The example of a few Ag atoms in the presence of a Si sp³ orbital is given as a simple illustration.