Momentum density and Compton profile of the inhomogeneous interacting electronic system. I. Formalism

A general formalism to determine the momentum density and Compton profiles of an inhomogeneous interacting electron system is proposed. The method is based on Feynman's theorem and the Hohenberg-Kohn theory of the inhomogeneous electron gas. Functional-derivative techniques are used. The results emcompass many of the previous approaches as special cases and present them from a unified viewpoint. In addition, several new approximate methods for calculating the Compton profiles of electronic systems are proposed.