Self-diffusion of component atoms and order-order relaxations in a B2-ordering binary system AB showing a tendency to triple-defect formation were consistently simulated by means of two Monte Carlo techniques. In view of a strict correlation between antisite-defect and vacancy concentrations the kinetic Monte Carlo simulations were implemented with a temperature-dependent vacancy concentration determined by means of semi-grand canonical Monte Carlo simulations. The Ising model of the system was completed with local-configuration-dependent saddle-point energy parameters related to vacancy mediated atomic jumps. The simulations elucidated the atomistic origin of the experimentally observed low rate of order-order relaxations in NiAl, as well as reproduced the experimental relation between the activation energies for order-order kinetics and Ni self-diffusion in NiAl. Higher value of the deduced activation energy for atomic migration with respect to the effective energy barriers related to individual atomic jumps indicated their high correlation.

Self-Diffusion and Order-Order Kinetics in B2-Ordering AB Binary Systems with a Tendency for Triple-Defect Formation: Monte Carlo Simulation. P.Sowa, R.Kozubski, A.Biborski, E.V.Levchenko, A.V.Evteev, I.V.Belova, G.E.Murch, V.Pierron-Bohnes: Philosophical Magazine, 2013, 93[16], 1987-98