CORRELATION-EFFECTS FOR POSITRON-ANNIHILATION WITH CORE AND SEMICORE ELECTRONS

We present a theory for calculating the momentum distribution of annih ilating electron-positron pairs in solids. The theory leads to a schem e in which the momentum density within the independent particle model for a given electron state is weighted by the annihilation rate of tha t state. The annihilation rate is calculated within the generalized gr adient approximation. The scheme describes the suppression of the elec tron-positron correlations due to the charge inhomogeneity and explain s the trends observed for positron annihilation with core and semicore electrons.