ACCURATE MOLECULAR ELECTROSTATIC POTENTIALS BASED ON MODIFIED PRDDO MWAVE-FUNCTIONS .2. ELECTROSTATIC POTENTIALS INSIDE THE MOLECULAR VAN-DER-WAALS ENVELOPE/

In part I of this series, the PESP (parameterized electrostatic potent ial) method was described and applied to the calculation of electrosta tic-potential-derived charges for a wide variety of organic and inorga nic systems. Based on PRDDO/M wave functions and parameterized against ab initio MP2/6-31G* calculations, PESP is an order of magnitude fas ter than nb initio STO-3G calculations, while achieving a level of acc uracy 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 d escribed. For a collection of 48 molecules and 55 distinct lone pair m inima, PESP yields the location and depth Rf lone pair minima to an av erage 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 o f 0.08 Angstrom and 1.5 kcal/mol. PESP electrostatic potential maps ar e, in some cases, virtually indistinguishable from those obtained at t he MP2/6-31G* level. (C) 1997 John Wiley & Sons, Inc.