Two-component density-functional calculations for positrons trapped by defects in solids

We present results of two-component density-functional calculations for electron systems with a localized positron. The theory is implemented 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, including the positron induced relaxation, have been determined in this scheme by first-principles molecular-dynamics methods. Positron states localized at vacancies in metals have been calculated using the tight-binding linear muffin-tin-orbital method within the atomic-spheres approximation as well as using the full-potential linear muffin-tin-orbital method. Calculations have been performed for positron lifetimes, core annihilation lineshapes and two-dimensional angular correlation maps. The results are compared with experiment.