Correlation effects for electron-positron momentum density in solids

A method describing the calculation of the momentum density of annihilating electron-positron pairs in solids has been developed. One-electron states, which are not perturbed by the positron, are used. The effects due to the enhancement of the electron density near the positron are taken into account by a factor depending on the electron state in the annihilating pair. This enhancement is used both for the valence and core electron states. The calculated momentum densities are in good agreement with the two-dimensional angular correlation of the annihilation radiation measurements in defect-free Cu and GaAs.