4-Center STO Interelectron Repulsion Integrals With Coulomb Sturmians

We present a method for evaluating 4-center electron repulsion integrals (ERI) for Slater-type orbitals by way of expansions in terms of Coulomb Sturmians. The ERIs can then be evaluated using our previously published methods for rapid evaluation of Coulomb Sturmians through hyperspherical harmonics. Numerical investigations are made of the efficiency in 1- and 2-center cases where the exact integrals can be evaluated. technology. This is due to the ease with which many-center interelectron repulsion integrals may be evaluated when Gaussians are used as a basis. In the present chapter, as in a number of our previous papers, we hope to contribute to a growing body of work whose aim is to increase the speed, ease of use, and popularity of ETO calculations. Success in this effort will open the doors to more accurate molecular calculations than those that can achieved using Gaussians as a basis.