NATURAL ENERGY DECOMPOSITION ANALYSIS - THE LINEAR-RESPONSE ELECTRICAL SELF-ENERGY

An extension of the natural energy decomposition analysis (NEDA) is de scribed that leads to a reduced, three-component treatment of ab initi o molecular interaction potentials. These components include the class ical electrical (static and induced) and quantum mechanical core (sigm a-sigma) and charge transfer (sigma-sigma) interactions. The electric al component is, in turn, represented by three terms: the static inter action of unperturbed fragment charge densities, a contribution involv ing polarized charge densities, and an electrical self polarization en ergy. Extended basis set calculations demonstrate the high numerical s tability of the three-component NEDA approach. Applications are presen ted for the Li+(H2O) and water dimer complexes. The long-range behavio r of the interaction potentials of these complexes is entirely determi ned by the classical electrical interaction of the fragments. Core and charge transfer effects are only significant for molecular separation s within roughly 1 Angstrom of equilibrium.