Monte-Carlo simulation of order-disorder kinetics in 2D and fcc binary alloys

The thermodynamic parameters that drive the atomic migration in 2D and 3D b inary alloys are studied using Monte-Carlo simulations. The model is based on a vacancy-atom jump mechanism between nearest neighbour sites, with a co nstant vacancy concentration, so that only the migration counterpart (E-M) Of the total activation energy (E-A = E-M + E-F, where E-F is the vacancy f ormation energy) is determined. The ordering kinetics are well described by exponential like behaviours with one (respectively two) relaxation time in the 2D (respectively 3D) cases. The temperature dependence of the long rel axation time is an Arrhenius law yielding effective migration energies, Slo wing down of the relaxation is observed at the Order-Disorder transitions. In both cases, we observe a linear variation of the effective migration ene rgy with the Order-Disorder critical temperature. (C) 2000 Elsevier Science B.V. All rights reserved.