It was recalled that Kuramoto et alia had calculated the activation energy, for dislocation-loop migration, by integrating the force-distance curve. Their method had great potential for the determination of migration energy in many situations. However, the validity of the method for point-defect migration had not yet been proved because the migration of point defects was a thermally activated process, and the physical meaning of the force in the force–distance curve had not been clarified. Here, its validity was investigated by using 3 methods to calculate the vacancy migration energy. In the first method, the migration energy was obtained by definition from the difference in potential energy between the equilibrium configuration before migration and the saddle-point configuration by using a statistical lattice relaxation method. The second method involved a molecular dynamics simulation which was based upon an absolute reaction-rate theory. The third method involved integration of the force–distance curve obtained by using the above statistical lattice relaxation method. The calculation model used was a 2-dimensional hexagonal lattice, with the Morse potential for Cu. The migration energies obtained by using the 3 methods were 0.391eV, 0.394eV and 0.392eV, respectively. As these values were similar, the validity of the third method was confirmed.

Validity of Activation Energy for Vacancy Migration Obtained by Integrating Force–Distance Curve. M.Matsushita, K.Sato, T.Yoshiie, Q.Xu: Materials Transactions, 2007, 48[9], 2362-4