VESPA: A new, fast approach to electrostatic potential-derived atomic charges from semiempirical methods

An improved semiempirical method for computing electrostatic potential-derived atomic charges is described. It includes a very fast algorithm for the generation of the grid points around the molecule and the calculation of the electrostatic potential at these points. The dependency of the atomic paint charges obtained on the number of grid points used in the fitting procedure is examined. For ''buried'' atoms a high density grid is necessary. It is possible to obtain 6-31G*-quality atom-centered point charges, even for phosphorus compounds, using AM1 or PM3. This approach can therefore be recommended for general use in QSAR or molecular mechanics for any organic and bioorganic system up to about 200 atoms. (C) 1997 by John Wiley & Sons, Inc.