One-center multipole calculation of second-order perturbation energies for H2+

Description

A knowledge of the H(1s) pseudospectrum allows one to calculate the one-centre second-order perturbation energies for the H(1s)-H+ interaction. The efficiency of such calculations is tested in detail for induction, exchange-induction, first-order overlap and Murrell-Shaw-Musher-Amos second-order energies for the ground and excited state H2+ at different internuclear distances. It is found that a large number of STO functions accounting for at least the first sixteen non-expanded multipoles is needed to obtain three figure accuracy in the short to medium range of internuclear separations. Higher accuracy can be obtained only in terms of a sensibly smaller number of two-centre functions which automatically satisfy the electron-nucleus cusp requirement.

Additional details