Effect of the [001] surface of Cu 3Au on the order-disorder transition

Abstract

Atomistic simulations of the two possible [001] surfaces of Cu 3Au are performed for temperatures below the transition temperature. The method apply the constant temperature, pressure and chemical potential difference Monte Carlo method, while the potential is the N-body tight-binding in the second-moment approximation. At T=0 K the two possible [001] surfaces have very different surface energies and the results agree with previous calculations. On the other hand the relaxation of the first layer for both cases is outwards and of similar magnitude. For temperatures 20% below the transition temperature we observe segregation of Au to the first surface atomic plane independent from the initial surface termination. Also, one can observe that the layers close to the surface exhibit below the transition temperature more disordering than the bulk material. The results are discussed in terms of known experimental results and theoretical results.