Computer-generated formulas for four-center integrals over slater-type orbitals

A triple infinite sum of formulas is generated by a computer algebra implementation of the Löwdin α function method (supplemented by a C matrix with integer elements that characterize an orbital) for a fourcenter two‐electron repulsion integral over 1s Slater‐type orbitals, with screening constants of 1. In this example, one orbital is placed at the origin and the others at equal distances along the x, y, and z axes. Surprisingly few terms are needed for five figure accuracy. There should be no problem in generalizing these methods to all cases of four‐center integrals.