Expansion formulae for two-center charge densities of integer and noninteger n generalized exponential type orbitals applied to evaluation of multicenter multielectron integrals

The series expansion formulae in terms of complete orthonormal sets of I (alpha) -exponential type orbitals introduced by the author are derived for the two-center charge densities of integer and noninteger n generalized exponential functions. The expansion coefficients arising in these relations are the multicenter overlap integrals of three I (alpha) -functions. The charge density expansion formulae obtained are utilized for the evaluation of multicenter multielectron integrals appearing in the Hartree-Fock-Roothaan and explicitly correlated theories when the generalized exponential type orbitals are employed as basis functions.