Interelectronic counter-balance and coalescence densities for the [formula omitted] ( n

Abstract

Explicitly correlated wave functions, expanded in basis sets of 200 Slater-Hylleraas exponential geminals, are reported for the n 1 S ( n<7) states of the helium isoelectronic sequence. The variational energies are no more than two nanohartrees above the exact ones. The electron–electron cusp condition is satisfied to an average of 1.8%. The wave functions are used to calculate the interelectronic counter-balance, E(0), and coalescence, I(0), densities. The inequality E(0)≥8 I(0), which is rigorously true in Hartree-Fock theory, is satisfied in all 55 correlated cases considered in this work. The ratio 8 I(0)/ E(0) is shown to be a smooth and sensitive measure of electronic correlation in these states.