Ordering kinetics in L12 and L10 structures via a general Monte-Carlo approach

Ordering kinetics in L1(2) and L1(0) structures are investigated through Monte-Carlo simulations using the model previously developed for B2 and DO3 structures : a vacancy jump mechanism between nearest neighbour sites with a Glauber algorithm using an Ising Hamiltonian. General tendencies have been explored with pair interaction energies between first (V-1) and second (V-2) nearest neighbours. Ordering kinetics are well described by exponential like behaviours with two relaxation times. Without a saddle point energy, the temperature dependence of the long relaxation time follows an Arrhenius law that yields an effective migration energy (E-M) that represents the influence of long range order on the atom migration energy. For a given value of V-1, E-M increases linearly with T-C, the order-disorder transition temperature. For the same set of parameters, E-M and its slope with T-C are much higher in the L1(2) structure than in the L1(0) one, in agreement with experimental trends observed in the Co-Pt and Ni-Pt compounds. The contribution of order to the migration energy has been calculated in some L1(2) phases where the pair interactions have been measured.