On the Reliability of Various Enhancement Theories for a Description of Electron-Positron Densities in Metals

Four theoretical approaches to calculate momentum densities of electron-positron annihilation pairs (MDAP) in crystalline solids are confronted with 3D densities reconstructed from two-dimensional angular correlation (2D-ACAR) data for copper, chromium, and yttrium. It is shown that the Bloch-modified ladder theory, in contrast to other approaches, is able to describe - at least qualitatively - the MDAP profiles for all metals investigated.