Densities of Valence Electrons in Simple Metals Effective with Respect to Electron-Positron Correlations

Abstract

In studies of momentum densities of electron-positron 2γ annihilation quanta p(p) in real metals, the local density approach (LDA) has been recently quite often applied (for reviews see, e.g., [1]). The results for annihilation characteristics obtained within LDA, however, are as reliable as far the assumed electron—positron correlation functions following from the electron gas theory are correct. Experimental positron annihilation data in simple metals would allow for verification of annihilation parameters in jellium obtained within various theories (reviewed in [1]). The problem is how to state the density of electron gas in real metal in order to compare experimental and theoretical correlation functions, and how far this comparison is possible. In this work we show that for valence electrons in simple metals the effective densities of an electron gas are well defined and may be determined in an unique way. As the result, the whole shape of p(p) inside the central Fermi surface (FS) may be determined, basing on the independent particles model (IPM) results and electron-positron enhancement factors in an electron gas, ejell (p, rseffs), if only the effective density parameter r seff is known.