The lifetimes of positrons which were captured by vacancies were calculated on the basis of the 2-component local density approximation for positrons and electrons. This first-principles calculation reproduced the experimental lifetimes in the bulk, and in mono- and di-vacancies, to within an error of 5%. It was found that the calculated lifetimes for multi-vacancies were much shorter than the experimental values. A new interpretation of the measured lifetimes for multi-vacancies was proposed.

M.Saito, A.Oshiyama: Materials Science Forum, 1995, 196-201, 1135-40