The effect of the positron distribution and electron–positron correlations on theelectron–positron momentum density for SiC

Abstract

To interpret the data on positron annihilation in solids in terms of the electron momentumdensity, both the electron–positron interaction and the positron distribution have to beconsidered explicitly. In this work we discuss the influence of the shape of the positronwavefunction and electron–positron (e–p) correlations on the calculated e–p momentumdensity and lifetime of the positron in perfect SiC. It is shown that the form of the positrondistribution in the Wigner–Seitz cell has a considerable effect on the calculated annihilationcharacteristics. The results obtained within the independent particle model are comparedwith their counterparts incorporating e–p correlation functions locally and beyond the localdensity approximation. The calculations have been performed for SiC of 3C cubic(zinc-blende) structure within the linear muffin-tin orbital atomic sphere approximationmethod.