An unconventional scf method for calculations on large molecules

Abstract

AbstractAn unconventional SCF method for calculations on large molecules with more than 100 basis functions is described. Storage problems which arise in conventional SCF schemes when storing more than 107 integrals are avoided by repeated calculation of integrals. The resulting increase in computational times is kept at a reasonable level by (a) improving the initial guess, (b) accelerating convergence, (c) employing a recursive construction of the Fock matrix, and (d) eliminating insignificant integrals from the calculation by a density‐weighted cutoff criterion. Sample calculations show that, compared with conventional SCF calculations, computational times increase by 25%–75% depending on the basis set and the shape of the molecule.