Saddle-point energies and Monte Carlo simulation of the long-range order relaxation in CoPt

Abstract

Abstract. We present atomic-scale computer simulations in equiatomic L10-CoPt where Molecular Dynamics and Monte Carlo techniques have both been applied to study the vacancy-atom exchange and kinetics relaxation. The atomic potential is determined using a Tight-Binding formalism within the Second-Moment Approximation. It is used to evaluate the different saddle-point energies involved in a vacancy-atom exchange between nearest-neighbour sites. The potential and the saddle-point energies have been used to simulate the relaxation of the long-range order in CoPt using a Monte Carlo technique. A vacancy migration energy of 0.73 ± 0.15 eV and an order-disorder transition temperature of 935 K have been found. PACS

Tuning ofL10atomic order in Co-Pt nanoparticles:Ab initioinsights

“…77 Nevertheless, we consider the obtained cluster expansion to be reliable for qualitative estimation of configurational effects within the most technologically interesting region of low/medium temperatures. In other theoretical simulations of Co-Pt, 25,26,[78][79][80][81][82] the predicted bulk order-disorder transition temperatures are substantially lower than those measured experimentally.…”

Modification of Pt/Co/Pt film properties by ion irradiation

“…It was, however, pointed out [26] that the classical empirical potentials can, in principle, describe the right behavior of magnetic systems by including specific correction terms responsible for magnetic interactions. This idea is supported by various MC calculations of the order-disorder transition in Co-Pt alloys using classical potentials: the modified embedded-atom method (MEAM) [27,28] and tightbinding second-moment approximation (TB-SMA) [28][29][30]. These potentials were developed without a magnetic term, but it was assumed that the energy state of the ordered phases (L1 0 ,L1 2 ) is lower than that of the chemical disordered fcc phase (A1) and the energy difference correlates with the transition temperature T t as E ≈ k B T t , where k B is the Boltzmann constant.…”

Thermodynamic stability of nanometre-sized Cu3Au systems

“…The order-to-disorder transition is abrupt in bulk samples, but becomes smoother in nanometre-sized systems [8][9][10][11][12]. In both cases, experimental as well as theoretical and numerical evidences suggest that the transition proceeds according to a nucleation and growth mechanism governed by vacancymediated diffusion processes, giving rise to a competition between ordering and disordering [13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”