Multi-configurational self-consistent field
| Electronic structure methods |
|---|
| Valence bond theory |
|
Coulson–Fischer theory Generalized valence bond Modern valence bond theory |
| Molecular orbital theory |
|
Hartree–Fock method Semi-empirical quantum chemistry methods Møller–Plesset perturbation theory Configuration interaction Coupled cluster Quantum chemistry composite methods Quantum Monte Carlo |
| Density functional theory |
|
Time-dependent density functional theory Thomas–Fermi model Orbital-free density functional theory Adiabatic connection fluctuation dissipation theorem Görling-Levy pertubation theory Optimized effective potential method Linearized augmented-plane-wave method Projector augmented wave method |
| Electronic band structure |
|
Nearly free electron model Tight binding Muffin-tin approximation k·p perturbation theory Empty lattice approximation GW approximation Korringa–Kohn–Rostoker method |
Multi-configurational self-consistent field (MCSCF) is a method in quantum chemistry used to generate qualitatively correct reference states of molecules in cases where Hartree–Fock and density functional theory are not adequate (e.g., for molecular ground states which are quasi-degenerate with low-lying excited states or in bond-breaking situations). It uses a linear combination of configuration state functions (CSF), or configuration determinants, to approximate the exact electronic wavefunction of an atom or molecule. In an MCSCF calculation, the set of coefficients of both the CSFs or determinants and the basis functions in the molecular orbitals are varied to obtain the total electronic wavefunction with the lowest possible energy. This method can be considered a combination between configuration interaction (where the molecular orbitals are not varied but the expansion of the wave function is) and Hartree–Fock (where there is only one determinant, but the molecular orbitals are varied).
MCSCF wave functions are often used as reference states for multireference configuration interaction (MRCI) or multi-reference perturbation theories like complete active space perturbation theory (CASPT2). These methods can deal with extremely complex chemical situations and, if computing power permits, may be used to reliably calculate molecular ground and excited states if all other methods fail.