Complete active space self-consistent field. A type of MCSCF calculation in which the configurations are chosen to be all those obtainable (i.e., full CI ) using a specified number of electrons and a specified set of orbitals. The set of orbitals is called the "active space," and the specified electrons are called "active." In many cases, it requires experience and skill to select the active space correctly.

Complete-Active-Space SCF method of solution of the electronic Schrödingerequation [ ROOS (1980)].

(Complete Active Space Self-Consistent Field) popular variant of the MCSCF method, using a specific choice of configurations. One selects a set of active orbitals and active electrons, then forms all of the configurations possible by placing the active electrons in the active orbitals, consistent with the proper spin and space symmetry requirements. Essentially equivalent to the FORS method.