Analytic techniques for the coupled multiconfiguration SCF perturbation theory

✍ Scribed by Michal Jaszuński; Andrzej J. Sadlej

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 703 KB
• Volume: 11
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560110204

✦ Synopsis

Abstract

The perturbation theory based on the paired excitation multiconfiguration self‐consistent field approach of Clementi and Veillard is considered. The coupled first‐order perturbed orbital equations are analysed and an appropriate computational scheme for their solution is discussed. The proposed computational scheme is analogous to the technique employed for the solution of the coupled Hartree–Fock equations in the one‐configuration approximation. However, because of the presence ofnondiagonal Lagrangian multipliers and the use of different one‐electron operators for different orbitals, the present scheme raises some new computational problems. In this context a new technique for the solution of the unperturbed multiconfiguration self‐consistent field equations is proposed. A simple illustration of the superiority of the multiconfiguration perturbation approach with respect to the ordinary coupled Hartree–Fock scheme is given. Also the validity of the variation formulation of the presented scheme and its relation to the finite‐field approach are discussed.