Positron annihilation in metal-vacancy—hydrogen complexes

Using a self-consistent density-functional theory we find that a positron is bound to a metal monovacancy even if it contains a hydrogen atom. While the positron binding energy in the hydrogen-vacancy complex does not differ markedly from that in a pure vacancy, the corresponding lifetimes and angular correlation curves are quite different from those in bulk as well as in pure vacancies. The implications of these results are discussed.