Two-Component Density Functional Study of Positron-Vacancy Interaction in Metals and Semiconductors

The positron-vacancy interaction in metals and semiconductors has been studied by the two-component density-functional-theory formalism. If a positron is not trapped at the vacancy, atoms surrounding the vacancy show inward relaxation for most cases except for nitrides, where outward relaxation is observed. The presence of positron suppresses the inward relaxation. Positron lifetimes have been calculated with and without the positron effect. The difference between two lifetime values is investigated in relation to the bulk modulus.