Orbitally ordered configuration-interaction calculations on small radicals. NH2 and BeH

Abstract

The orbitally ordered configuration-interaction (CI) method of Cooper and Pounder is applied to two small radicals. Among the operators used here to generate modified virtual orbitals, the empirical operator, h_F+γK^val₀, is shown to be the best. The parameter γ has the value –15 for both these radicals, one of which is of σ symmetry and the other of π symmetry. It is significant that the same value of γ was found elsewhere for closed-shell molecules using an analogous operator.