Order and Migration Energies in a CoPt_3 Single Crystal: Experimental Determination from Neutron Scattering and Monte-Carlo Simulations

摘要

The phonon dispersion curves have been measured in a CoPt_3 single crystal using inelastic neutron scattering. Measurements were performed at room temperature and at 930 K in the Li_2 ordered structure and at 1060K in the disordered state. The average migration energies EM of the ordered (E_M~O= 1-36 eV) and disordered states (E_M~D =1.13 eV) are deduced from the phonon density of states. Moreover, the contribution to the migration energy of the effective pair interaction energies that determine the stability of the ordered phase is obtained through a Monte Carlo simulation based on an atom-vacancy jump model, using the five interactions deduced from the analysis of the elastic neutron diffuse scattering cross-sections. The obtained value of 0.25 eV is in very satisfying agreement with the difference (E_M~O?- E_M~D) got experimentally.