New multicentre point charge models for molecular electrostatic potentialsfrom semiempirical MO-calculations

Two quasi-multipole electrostatic models for molecular charge distributions are presented. They assign arrays of point charges to nonhydrogen atoms on the basis of hybrid orbitals or localised molecular orbitals. When used wi th common semiempirical MO-techniques, they reproduce natural atomic orbita l derived point charge (NAO-PC) and ab initio molecular potentials well. Th e localised orbital technique (LMO-PC) is intuitively more attractive than the hybrid orbital-point charge (HO-PC) method, although the former is more CPU-intensive.