COMPARISON OF NDDO AND QUASI-AB INITIO APPROACHES TO COMPUTE SEMIEMPIRICAL MOLECULAR ELECTROSTATIC POTENTIALS

The suitability of the two most widely used strategies to compute semi empirical MEPs is examined. For this purpose, MEP minima, electrostati c charges, and dipoles for a large number of molecules were computed a t the AM1, MNDO, and PM3 levels using both the NDDO strategy developed by Ferenczy, Reynolds, and Richards and our own quasi-ab initio metho d. Results demonstrate that the quasi-ab initio is preferred over the NDDO method for the computation of MEP minima. It is also found that t he best set of semiempirical charges and dipoles are obtained using ei ther the AM1 NDDO or the MNDO quasi-ab initio methods. In these two ca ses, the quality of the results is fully comparable with 6-31G values . (C) 1994 by John Wiley and Sons, Inc.