Use of a nonlocal density approximation for transformation from electron density to electron momentum density

Abstract

A new method to extract atomic electron momentum density from the corresponding electron density has been proposed. The method is based upon the nonlocal density approximation (NLDA) due to Gunnarsson, Jonson, and Lundqvist; and to Alonso and Girifalco. The reduced first order density matrix Γ (r/r') is estimated from the atomic electron density ρ (r) by use of an averaged density distribution, ρ (r). The Γ(r'/r'+r) thereby obtained is integrated out to obtain the autocorrelation function B(r) enabling evaluation of electron momentum density γ (p) and <pⁿ> values. The method has been developed for spherically symmetric densities and has been tested out for beryllium, nitrogen, neon, and argon atoms. The <pⁿ> values and momentum densities thus obtained are in a very good agreement with the corresponding Hartree-Fock counterparts.