Atomic and molecular energies in terms of electrostatic potentials at nuclei

Several formulas, both exact and approximate, that relate atomic and molecular energies to electrostatic potentials at nuclei are discussed in terms of the relative contributions of the nuclear-electronic, nuclear-nuclear, and electronic-electronic interactions. These quantities and related ratios are evaluated at the density functional B3PW91/6-311+G(3df,2pd) level for a group of 24 molecules. A modified version of an approximate molecular energy expression is tested and found to give improved results. (C) 2002 Wiley Periodicals, Inc.