Multipole expansions of orbital products about an intermediate center

A numerical method described previously (Talman, Int J Quantum Chem, 2007, 107, 1578) is reviewed and a modified formulation that may be more computationally efficient is presented. Modifications required for the application to real harmonics are described. The method requires the numerical evaluation of a one‐dimensional integral on a finite interval, and an improved method for this is described. The application to the evaluation of electron–electron repulsion four‐center integrals is also discussed. It is indicated that μ H accuracy is obtainable with modest computational effort. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011