ADDITIONAL CONDITION FOR TRANSFERABILITY IN PSEUDOPOTENTIALS

The chemical property of hardness is extremely important in the correc t prediction of electron transfer between reacting chemical systems. H ardness is defined to be one-half the second derivative of the total e nergy of a chemical system with respect to the number of electrons. Th e requirement that the total energies of atom and pseudoatom match to second order with arbitrary changes in valence-state occupancy yields major decreases in the errors made when using psudopotentials. The con cept also clarifies the role of core density in pseudopotential applic ation. A practical prescription is presented for generating such pseud opotentials and their corresponding core densities, and several ab ini tio results are compared with those of high-quality norm-conserving ps eudopotentials. Significant improvements are found.