General second-order MCSCF theory for large Cl expansions

Second-order MCSCF theory is presented in a fashion which is capable of treating large Cl expansions. This formalism is then extended to encompass a state-average MCSCF procedure. Sample calculations on Mo2 and the ethyl radical, which involve 1698 and 2302 CSFs, respectively, are presented and a number of approximate schemes discussed. © 1982 American Institute of Physics.