Fitting the Coulomb potential variationally in Xα molecular calculations

The method of Mintmire and Dunlap which variationally fits the Coulomb potential rather than the charge density is extended to linear combination of Gaussian-type orbitals Xα calculations on molecules. This approach is more efficient than fitting the charge density since the same integrals are used to treat the Coulomb and exchange potentials. Furthermore, the required Fock matrix elements are simple overlap rather than Coulomb integrals. However, the method is somewhat less accurate than fitting the charge density in a test on H2