NONLOCAL ELECTRON-POSITRON CORRELATIONS IN SOLIDS WITHIN THE WEIGHTEDDENSITY 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 enhancem ent factors is discussed. The calculated WDA electron-positron enhance ment factors for the core electrons are compared with those obtained w ithin the local-density approximation. Also, differences in the electr on-positron enhancement factors due to the s, p, d, and f angular mome ntum channels of the electron charge density are studied. The influenc e of the electron-positron interaction on the positron density distrib ution in solids is discussed. The formalism is applied to ab initio ca lculations of positron lifetimes in a variety of metals and silicon. T he influence of various approximations to the electron-positron intera ction 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 annih ilation rates and lifetimes. The results are compared to those calcula ted within the local-density approximation and the generalized gradien t approximation. [S0163-1829(48)06037-8].