Use of energy constraint for refinement of electron momentum distributions

Abstract

A procedure based on the calculus of variations to refine a given electron momentum density with the constraints of the given number of electrons and a prescribed <p²> expectation value has been developed. This procedure has been tested with near-Hartree-Fock (NHF) electron momentum density data employed as initial distributions for the atoms beryllium through neon. The constraints of the corresponding CI-theoretical and experimental energy values have been imposed. In all cases, the values of the refined electron momentum density at p=0 and the peak value of the Compton profile J(0) are lower than the corresponding NHF ones. This lowering of J(0) value is generally in conformity with the corresponding results from CI and MC-SCF calculations. The present procedure is seen to simulate well the electron momentum densities and <p^-1> as well as <p> expectation values obtained from correlated wave functions without ever doing extra quantum mechanical calculations.