Numerical methods of the preliminary evaluation of the role of admixed configurations in atomic calculations

Methods of the preliminary evaluations of the averaged energy correlation corrections and averaged configuration mixing weights arising from the separate admired configurations are presented in this paper. These methods are based on the usage of the second order of the perturbation theory and analytical expressions of the sums of the squares of the interconfigurational matrix elements and the averaged energy differences between configurations. Two possible ways to average these energy differences are discussed. Large number of calculations for different atomic states shows a good agreement of the preliminary evaluations with averaged results from diagonalization of energy matrices. (C) 2001 Elsevier Science B.V. All rights reserved.