Nonlocal electron-positron correlations in solids within the weighted density approximation

Nonlocal electron-positron correlation effects in solids are studied. The weighted density approximation (WDA) is applied to calculations of the nonlocal state-selective electron-positron correlation functions. The importance of state selectivity of the electron-positron enhancement factors is discussed. The calculated WDA electron-positron enhancement factors for the core electrons are compared with those obtained within the local-density approximation. Also, differences in the electron-positron enhancement factors due to the $s,$ $p,$ $d,$ and f angular momentum channels of the electron charge density are studied. The influence of the electron-positron interaction on the positron density distribution in solids is discussed. The formalism is applied to ab initio calculations of positron lifetimes in a variety of metals and silicon. The influence of various approximations to the electron-positron interaction on the positron lifetimes is also presented. Moreover, we study how the core electrons as well as different angular momentum channels of the valence electron density contribute to the total positron annihilation rates and lifetimes. The results are compared to those calculated within the local-density approximation and the generalized gradient approximation.