Multiconfiguration wave functions for highly excited states by the generalized brillouin theorem method

Abstract

A multiconfiguration method is presented which can yield upper bounds to the energies of excited states within the single- or many-configuration approximation, and which shows quadratic convergence behavior. As an example, test calculations on valence and core excited states of the Li atom are discussed. The method is then applied to investigate molecular hole states. (I) Two kinds of correlation effects occur in core hole states of symmetiical molecules: in addition to the already known correlation effect, polarization of the valence. shell by a localized hole, there is still another kind of correlation effect, core-core reorganization, of the order of about 1 eV. (2) When the analogous core model is used to interpret core excited states, three. corrections have to be taken into consideration: in addition to the difference in ground-state geometries and the difference in exchange interactions, one must also correct for the difference in screening of the cores.