Experimental determination of pair interaction energies in aCoPt3single crystal and phase-diagram calculations

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

“…Considering the temperature range (600-980 K) and the goal of our simulations, the approximation of interactions up to the second nearest-neighbours is rather justified. Furthermore, x-ray and neutron diffuse scattering measurements have been used in conjunction with inverse cluster variation method to calculate the effective pair interactions in L1 2 -Co 3 Pt and in L1 2 -CoPt 3 [25,26]. In both systems the first and second interactions are the predominant ones.…”

“…This system has been studied extensively to understand the origin of the asymmetry in its phase diagram. Various explanations have been proposed: for example, an effect of many-body interactions [19], an influence of magnetism, and variations of atomic interaction with composition [25,26]. Calculation of this phase diagram may appear quite simple a priori, as it is based on the fcc lattice at almost all temperatures and compositions, but it still remains a challenge today.…”

Study of local order in FePd by neutron diffuse scattering

“…When the contrast related to the scattering lengths and the neutron absorption are favorable, the neutron diffuse scattering (NDS) remains the most powerful technique, mainly at high temperatures when the equilibrium state of local order is difficult to keep by quenching, because NDS allows high temperature in situ measurements. Several studies of the local atomic arrangement have been performed in systems where the phase diagram is well known, and could be reproduced satisfactorily using the deduced energetic parameters [1,2].…”

Diffuse scattering

“…Several extensive studies have been performed in the past, such as the investigation of ternary FeNiCr alloys [17], local order in CoPt [18] or FeV alloys [19], ordered vacancies in NiC [21] among others. A particular interesting case is the investigation of the diffuse scattering for a stoechiometric compound above the transition towards a LRO state.…”

“…It is well adapted to typical length scales of a few tens of unit cells. The second method, taking the random state as a reference, yields the determination of short range order nuclear parameters [1,13,[17][18][19][20], short range ordering of vacancies [21], local magnetic perturbations [22], local lattice distortions [2,21], or pair distribution functions [23]. It covers atomic or spin correlations mostly limited to near neighbor distances.…”