Collect. Czech. Chem. Commun. 1988, 53, 2308-2319

Calculation of electrostatic potentials and fields inside zeolite cavities

János G. Ángyána, György Ferenczya, Péter Nagyb and Gábor Náray-Szabóa

a CHINOIN Pharmaceutical and Chemical Works, H-1325 Budapest, P.O. Box 110, Hungary
b Chemical Works of Gedeon Richter Ltd., H-1475 Budapest, P.O. Box 27, Hungary


We present a modification of our bond increment method for the calculation of molecular electrostatic potentials and fields inside zeolite cavities. Introducing a variant of the Mulliken approximation for the off-diagonal matrix elements of the potential and optimizing the parameters of the modified formula, we achieved much better agreement with ab initio STO-3G minimal basis set results than with the original version. For a representative set of 10 small molecules the standard mean deviation between potentials calculated on the van der Waals surface with the ab initio and approximate methods is 9·1 kJ/mol. The relative error decreases from 21 to 9 per cent for the lone-pair regions of molecules modelling zeolite cavities. Applying the modified bond increment method for a realistic faujausite model we have found that the potential and field are almost exclusively of long-range origin. This means that, if using appropriate atomic charges, the monopole approximation gives correct results for electrostatic potentials and fields inside zeolite cavities.