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## Multi-configurational self-consistent field
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. ## Additional recommended knowledge
## IntroductionFor the simplest single bond, found in the H - ,
where N - ,
where Θ - .
This Hartree-Fock model gives a reasonable description of H Consequently, the HF model cannot be used to describe dissociation processes with open shell products. The most straightforward solution to this problem is introducing coefficients in front of the different terms in Ψ - Ψ
_{1}=*C*_{Ion}Φ_{Ion}+*C*_{Cov}Φ_{Cov},
which forms the basis for the valence bond description of chemical bonds. With the coefficients C - φ
_{2}=*N*_{2}(1*s*_{A}− 1*s*_{B}),
the total wave function of H - Ψ
_{MC}=*C*_{1}Φ_{1}+*C*_{2}Φ_{2},
where Φ ## Complete Active Space SCFA particularly important MCSCF approach is the ## Restricted Active Space SCFSince the number of CSFs quickly increases with the number of active orbitals, along with the computational cost, it may be desirable to use a smaller set of CSFs. One way to make this selection is to restrict the number of electrons in certain subspaces, done in the ## See also- Charlotte Froese Fischer
- Douglas Hartree
- Hartree-Fock method
## References**^**McWeeny, Roy (1979).*Coulson's Valence*. Oxford: Oxford University Press, 124 - 129.__ISBN 0-19-855145-2__.**^**Jensen, Frank (2007).*Introduction to Computational Chemistry*. Chichester, England: John Wiley and Sons, 133 - 158.__ISBN 0470011874__.**^**Cramer, Christopher J. (2002).*Essentials of Computational Chemistry*. Chichester: John Wiley & Sons, Ltd., 191 - 232.__ISBN 0-471-48552-7__.
## Further reading- Cramer, Christopher J. (2002).
*`Essentials of Computational Chemistry*. Chichester: John Wiley and Sons.__ISBN 0 471-48552 7__.
Categories: Quantum chemistry | Computational chemistry |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Multi-configurational_self-consistent_field". A list of authors is available in Wikipedia. |