title: Diffusion of muonium and hydrogen in diamond.
abstract: Jump rates of muonium and hydrogen in diamond are calculated by quantum transition-state theory, based on the path-integral centroid formalism. This technique allows us to study the influence of vibrational mode quantization on the effective free-energy barriers DeltaF for impurity diffusion, which are renormalized with respect to the zero-temperature classical calculation. For the transition from a tetrahedral (T) site to a bond-center (BC) position, DeltaF is larger for hydrogen than for muonium, and the opposite happens for the transition BC-->T. The calculated effective barriers decrease for rising temperature, except for the muonium transition from T to BC sites. The calculated jump rates are in good agreement with available muon spin rotation data.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Carlos P
authors.initials: CP
authors.lastname: Herrero
authors.forename: Rafael
authors.initials: R
authors.lastname: Ramírez