Molecular electrostatic properties using point charges: ab initio hybridization displacement charges combined with bond-centered charges

Abstract

A new approximate scheme to compute hybridization displacement charges (HDC) in molecules at the ab initio level using bond-centered charges arising due to overlapping atomic orbitals has been developed. It has been applied at the SCF/6-31G** and SCF-CIS/6-31G** levels to the ground and excited states, respectively, of several polar and non-polar molecules. It is found that, statistically speaking, HDC computed using the present approach reproduce SCF dipole moments and surface molecular electrostatic potential (MEP) patterns quite satisfactorily. In some cases, HDC reproduce MEP features even somewhat better than the MEP-fitted CHelpG charges, particularly in molecules where MEP values around atoms vary rapidly, e.g. around the boron atom in certain molecules containing it, and homonuclear diatomic molecules. Some interesting information about molecular bonding, not available from other charge distributions, is revealed by the present approach, e.g. in lithium containing molecules. The present approach also appears to describe molecular electrostatic properties and molecular bonding better than that where the Löwdin's symmetry orthogonalized atomic orbitals are used.