Cage motion of a probe atom in a vacancy complex in Pt

The perturbation function of a Cd probe atom bound in a hydrogen-decorated vacancy complex in Pt is found to exhibit dynamical relaxation at 294 K, as measured by the technique of perturbed γ-γ angular correlations. Based on other characteristics of the complex, a model is proposed for the structure of the complex. In the undecorated state, it consists of a probe atom at the center of a tetrahedron of vacancies in the fcc structure. In the decorated state at low temperature, the probe atom returns to one of the four vacant lattice sites. The relaxation at room temperature is attributed to motion of the probe atom in a cage formed by the four vacant sites.