A limited expansion method for electron repulsion integrals

Two center exchange and three center integrals required for MO calculations can be calculated very rapidly using a limited linear expansion of two center charge distributions including, for integrals involving second row atoms. only atomic orbitals up to n = 2. Results for the total energy and the dipole moment for BH, NH, FN, N-2, C-2, F-2, CO, BF and H2O are shown to be very close to the values obtained from accurate calculations using the same basis set.