Growth and lattice dynamics of Co nanoparticles embedded in Ag: A combinedmolecular-dynamics simulation and Mossbauer study

We use Mossbauer spectroscopy in combination with atomic scale modeling in order to gather a comprehensive understanding of the growth and the dynamic s of cobalt nanoprecipitates in silver. The modeling makes use of classical molecular dynamics in the canonical ensemble by means of the Rahman-Parine llo technique. Atomic interactions are governed by an embedded atom model, which is validated for the static Co-Ag interaction by means of a compariso n with extended x-ray absorption fine structure measurements and for the dy namical interaction with Mossbauer spectroscopy data. This allows us to ide ntify the cluster size dependent atomic arrangements at the cluster-matrix interface, where strong relaxation takes place. A detailed analysis of the Mossbauer spectra taken at two temperatures after annealing at different te mperatures allows us not only to characterize the cluster size dependence o f magnetic properties, but also to evidence a possible Ostwald ripening gro wth mechanism. The mean and interface Debye temperatures are deduced from t he Mossbauer spectra and found quite consistent with the model predictions. On this basis, the atomic scale modeling allows us to identify detail of a tomic vibrational properties as a function of distance from the cluster cen ter and a discontinuity of the vibration amplitudes at the precipitate-matr ix interface is evidenced.