An efficient first-order CASSCF method based on the renormalized Fock-operator technique

SummaryA new efficient first-order CASSCF method (multiconfiguration SCF (self consistent field) in a complete active space) is described. Its main characteristics are (i) use of the generalized Brillouin theorem (Fock-operator method), (ii) renormalization of single excitations, (iii) fast microiterations containing only two-index transformations, i.e. M3N2 steps. Convergence is generally reached in eight to twelve macroiterations. The method is applied to several examples (LiH, N2, AlO) and compared to other MCSCF (multiconfiguration SCF) methods.

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