MCSCF optimization through combined use of natural orbitals and the brillouin–levy–berthier theorem

作者：Klaus Ruedenberg, Lap Ming Cheung, Stephen T. Elbert · 发表于：International Journal of Quantum Chemistry · 年份：1979 · DOI：10.1002/qua.560160511 · 被引用次数：323 · 研究领域：Advanced Chemical Physics Studies、Magnetism in coordination complexes、Spectroscopy and Quantum Chemical Studies

Abstract A novel approach is developed for optimizing molecular orbitals within the context of a multiconfiguration self‐consistent‐field problem. The MCSCF wave function is determined through a sequence of eigenvalue problems in the multiconfiguration space and the single‐excitation space. They are used to iteratively improve the natural orbitals, which in turn are related, by successively improved transformations, to the MCSCF orbitals. The mathematical problems arising out of this general concept are solved and the computational implementation is discussed. In many applications the method has proven itself as a powerful approach in forcing rapid convergence. Adaptation to spin and spatial symmetry is maintained throughout and the procedure is applicable to excited states as well as to ground states.