Multi-configuration self-consistent field electron correlation methods

ELECTRON CORRELATION METHODS 4.6 MULTI-CONFIGURATION SELF-CONSISTENT FIELD 121... 

A more accurate method which serves as the basis to generate orbitals for higher-order electron-correlation effects is the complete active space multi-configuration self-consistent field (CAS-MCSCF or CASSCF) method. In this method, a set of the most active electrons, usually the valence electrons, are distributed in all possible ways... 

Aspects of the relativistic theory of quantum electrodynamics are first reviewed in the context of the electronic structure theory of atoms and molecules. The finite basis set parametrization of this theory is then discussed, and the formulation of the Dirac-Hartree-Fock-Breit procedure presented with additional detail provided which is specific to the treatment of atoms or molecules. Issues concerned with the implementation of relativistic mean-field methods are outlined, including the computational strategies adopted in the BERTHA code. Extensions of the formalism are presented to include open-shell cases, and the accommodation of some electron correlation effects within the multi-configurational Dirac-Hartree-Fock approximation. We conclude with a survey of representative applications of the relativistic self-consistent field method to be found in the literature. 

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