Parametrization of the correlation crystal field

Quite large discrepancies are found when crystal field splittings are fitted to a one-particle potential V= Sigma Anmynm. It is suggested that the parametrization of the experimental data can be improved by introducing an additional potential which represents the two particle correlation induced by the environment. This separates the problem of describing the discrepancies from the problem of explaining them in terms of specific mechanisms. A formal development of the correlation crystal field concept is given, and suggestions are made regarding the treatment of experimental data. Some possible generalizations of this concept are also discussed.