Systematically constructed two-electron Gaussians which are transferable between different atoms for ab initio CI calculations

Abstract

In order to prepare basis sets particularly well suited for the calculation of electron-pair correlation energies in molecular systems, two-electron functions are constructed from components which lead to integrals of adequate simplicity: i.e., from Gaussian functions representing the one-electron components, and with the aid of factors exp(−γ r 12 2) and of two parameters ( C 0, C 1). The one-electron functions are generated from four parameters ( A 0, A 1, A 2, A 3). With a transition from He to Li +, Be 2+, B 3+, C 4+, N 5+, O 6+, F 7+ Ne 8+, or H −, the reoptimization of a single parameter ( A 0) is sufficient to obtain an electronic energy of the same high precision (between 10 −6 and 10 −7 a.u. for a Cl dimension of 416) which results from a reoptimization of all six parameters.