Generalized Møller−Plesset Partitioning in Multiconfiguration Perturbation Theory

• Published in: Journal of chemical theory and computation Vol. 6; no. 7; pp. 2024 - 2033
• Main Authors: Kobayashi, Masato, Szabados, Ágnes, Nakai, Hiromi, Surján, Péter R.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 13.07.2010
• Subjects: Quantum Electronic Structure
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/ct1001939

Two perturbation (PT) theories are developed starting from a multiconfiguration (MC) zero-order function. To span the configuration space, the theories employ biorthogonal vector sets introduced in the MCPT framework. At odds with previous formulations, the present construction operates with the full Fockian corresponding to a principal determinant, giving rise to a nondiagonal matrix of the zero-order resolvent. The theories provide a simple, generalized Møller−Plesset (MP) second-order correction to improve any reference function, corresponding either to a complete or incomplete model space. Computational demand of the procedure is determined by the iterative inversion of the Fockian, similarly to the single reference MP theory calculated in a localized basis. Relation of the theory to existing multireference (MR) PT formalisms is discussed. The performance of the present theories is assessed by adopting the antisymmetric product of strongly orthogonal geminal (APSG) wave functions as the reference function.