Approximate Single-Center Perturbation Calculations. I. Ground States of H2+, HeH2+, H2, HeH+, He22+, and Linear Symmetric H3+

Abstract

Using the “molecular puff” equations as a starting point, first‐order perturbation equations are solved for H₂, HeH⁺, He₂², and linear symmetric H₃⁺, and first‐ and second‐order equations for H₂⁺ and HeH²⁺. The perturbation wavefunctions are expanded in partial waves and the resulting equations solved by numerical integration for the $\text{1sσ}$ ground states. The errors in the calculated energies are in the range 0.5–10.0 kcal/mol and represent a considerable improvement on similar calculations reported by Hauck, Kim, Parr, and Hameka [J. Chem. Phys. 47, 2677 (1967)].