Configuration average of general n-body symmetrical tensor operators

A new method for calculating configuration average of n-body operators is presented. The method is easily adapted for calculations of high spectral moments, average cross sections of atomic processes, etc. We present a general explicit expression for the dependence of the configuration average on the occupation numbers. An algorithm based on the angular momentum graphical technique is then applied to obtain the dependence of the average on the quantum numbers of the orbitals involved. This algorithm is easily adapted to numerical applications using a newly developed angular momentum code. A detailed analytic example is presented for the case of average of a three-body effective interaction.