Charge renormalization at the large-D limit for diatomic molecules

The charge renormalization procedure for the calculation of the correlation energy of atoms utilizing the analytically known large-D limit solutions for the exact and Hartree–Fock equations is extended to diatomic molecules. This procedure is based on the variation of the nuclear charge, Z , and internuclear distance, R , of the Hartree–Fock Hamiltonian such that the Hartree–Fock energy will be significantly closer to the exact energy. We calculate to first order in dZ the leading contribution to the correlation energy by changing the nuclear charge to some renormalized nuclear charge, Zi →Zi1dZi . To first order in dZ , this leads to an approximate expression, E(Za ,Zb ,R)5(]E /]Za)dZa1(]E /]Zb)dZb , for the correlation energy based on the charge renormalization parameter dZ , which is fixed systematically from the large-D limit. The theory is applied to diatomic molecules. Near the equilibrium, we are predicting the correlation energy typically with 80% or greater accuracy in a completely self-consistent and systematic way with no additional cost to the Hartree–Fock calculation. An improved approach to estimating the correlation energy for all R is outlined. © 1995 American Institute of Physics.