ACCURATE MOLECULAR ELECTROSTATIC POTENTIALS BASED ON MODIFIED PRDDO MWAVE-FUNCTIONS .1. ELECTROSTATIC POTENTIAL DERIVED ATOMIC CHARGES/

A new approach for the calculation of electrostatic potential derived atomic charges is presented. Based on molecular orbital calculations i n the PRDDO/M approximation, the new parametrized electrostatic potent ial (PESP) method is parametrized against ab initio MP2/6-31G* calcul ations. For a data set of 820 atoms in 145 molecules containing H, C, N, O, F, P, S, Cl, and Br (including hypervalent species), the PESP me thod achieves a mean absolute error of 0.037 e(-) with a correlation c oefficient of 0.990. Unlike other approximate approaches, no scaling f actor is required to improve the agreement between PESP charges and th e underlying ab initio results. PESP calculations are an order of magn itude faster than the simplest ab initio calculation (STO-3G) on large molecules while achieving a level of accuracy that rivals much more e laborate nb initio methods. (C) 1997 by John Wiley & Sons, Inc.