Positron lifetime in Si and GaAs treated using the density-gradient-correction methods

Abstract

The positron lifetimes in bulk Si and GaAs are calculated using the electron and positron densities obtained from the first principles method. The electron density is obtained in the pseudopotential method with the exchange-correlation, potential treated in both the generalised gradient approximation (GGA) and local density approximation (LDA). The positron density and the enhancement factor are also obtained using GGA methods. The positron lifetimes obtained using calculated lattice constants do not agree with the experiments. The theory is in agreement with the experiment only when the experimental lattice constants and the nonlinear core correlations are taken into account.