Two-Component Density Functional Calculations of Positron Lifetimes for Band-Gap Crystals

Lifetimes of positrons in perfect crystals having band gaps are calculated using the two-component density functional theory. For electron–positron correlation, we use the local density approximation (LDA) and the correction of the LDA using a high-frequency dielectric constant. While the LDA is found to slightly underestimate positron lifetimes, the correction of the LDA well reproduces experimental lifetimes. We discuss the quality of crystals used in a positron annihilation experiment by comparing theoretical and experimental positron lifetimes.