Efficient formulas for molecular integrals over the Hiller–Sucher–Feinberg identity using Cartesian Gaussian functions: Towards the improvement of spin density calculations

Recurrence relations are derived for the molecular integrals arising in the use of the Hiller–Sucher–Feinberg identity. In comparison with the formulas obtained by other methods, the present result gives simpler formulas, and efficient computations are feasible. To perform the numerical integration the double exponential formula developed by Takahashi and Mori is found suitable for accurate and expeditious calculations.