Accurate molecular electrostatic potentials based on modified PRDDO/M wave functions .2. Electrostatic potentials inside the molecular van der Waals envelope

In part I of this series, the PESP (parameterized electrostatic potential) method was described and applied to the calculation of electrostatic-potential-derived charges for a wide variety of organic and inorganic systems. Based on PRDDO/M wave functions and parameterized against ab initio MP2/6-31G** calculations, PESP is an order of magnitude faster than nb initio STO-3G calculations, while achieving a level of accuracy that rivals that of far more sophisticated ab initio methods. In this study, the application of the PESP method to the high potential regions of molecules containing I-I, C, N, O, F, P, S, Cl, and Br is described. For a collection of 48 molecules and 55 distinct lone pair minima, PESP yields the location and depth Rf lone pair minima to an average accuracy (relative to MP2/6-31G**) of 0.03 Angstrom and 2.5 kcal/mol, respectively. Similarly, the location and well depths of minima in the ir regions of organic molecules are calculated to an accuracy of 0.08 Angstrom and 1.5 kcal/mol. PESP electrostatic potential maps are, in some cases, virtually indistinguishable from those obtained at the MP2/6-31G** level. (C) 1997 John Wiley & Sons, Inc.