A practical approach to the computation of the electrostatic energy in large molecules

Abstract

A study of the reliability of the coulombic monopole-monopole model, especially when semiempirical electrostatic potential derived charges are used, in representing the exact electrostatic interaction energy is reported. Results presented in this work support the reliability of the coulombic monopole-monopole expression in reflecting the electrostatic interaction energy determined from the Morokuma decomposition scheme. The monopole-monopole model underestimates the electrostatic energy term, but the appropriate scaling by a factor of 1.425 permits reproduction of the exact electrostatic energy when electrostatic potential derived charges are considered. The reliability of the semiempirical electrostatic charges in reproducing not only the atomic charges derived from experimental data, but also the monopole-monopole electrostatic energy calculated from the 6-31G ∗∗ charges is also shown.