2-COMPONENT DENSITY-FUNCTIONAL CALCULATIONS FOR POSITRONS TRAPPED BY DEFECTS IN SOLIDS

We present results of two-component density-functional calculations fo r electron systems with a localized positron. The theory is implemente d into several electronic-structure calculation methods. For example, positron states at vacancies in semiconductors have been calculated in the pseudopotential plane-wave framework. The ionic relaxations, incl uding the positron induced relaxation, have been determined in this sc heme by first-principles molecular-dynamics methods. Positron states l ocalized at vacancies in metals have been calculated using the tight-b inding linear muffin-tin-orbital method within the atomic-spheres appr oximation as well as using the full-potential linear muffin-tin-orbita l method. Calculations have been performed for positron lifetimes, cor e annihilation lineshapes and two-dimensional angular correlation maps . The results are compared with experiment.