Atomic charges derived from semiempirical methods

TLDR

The authors scale MNDO‑derived ESP charges linearly (y = Mx) to preserve total charge. Semiempirical MNDO ESP charges, when linearly scaled, yield 6‑31G*–quality atomic point charges that agree well with ab initio ESP charges and outperform AM1, enabling efficient force‑field simulations.

Abstract

Abstract It is demonstrated that semiempirical methods give electrostatic potential (ESP) derived atomic point charges that are in reasonable agreement with ab initio ESP charges. Furthermore, we find that MNDO ESP charges are superior to AM1 ESP charges in correlating with ESP charges derived from the 6‐31G* basis set. Thus, it is possible to obtain 6‐31G* quality point charges by simply scaling MNDO ESP charges. The charges are scaled in a linear ( y = Mx ) manner to conserve charge. In this way researchers desiring to carry out force field simulations or minimizations can obtain charges by using MNDO, which requires much less computer time than the corresponding 6‐31G* calculation.