Stability of FePt, FePt3 Nanoclusters of Different Habits

 Calculations of the total energy of Fe-Pt nanoclusters, corresponding in the phase diagram to the compositions of FePt, FePt3 intermetallics and possessing either characteristic structures L10 and L12, respectively, or non-characteristic disordered structure A1, as well as various particle habits (cuboctahedra, icosahedra) are carried out by molecular dynamics for the first time. The dependences of cluster stability on their size and temperature are plotted, along with the schemes of temperature transformations of cluster morphology and the dependence of the melting points of the clusters with these structures and habits on their size. The size range (2–8 nm) corresponds to the sizes of particles observed by high-resolution electron microscopy. It is shown that the species play an essential part in the phase transformations proceeding under heating in the nanostructured system Fe-Pt and leading to the formation of nanocrystals with highly ordered L10 structure possessing giant coercivity are cubic nanoclusters with the ordered structures L10 and L12. With an increase in cluster size, their stability and melting points increase, tending to saturation of the dependencies within the size range above 10 nm. The least stable clusters are those of intermetallics with non-characteristic disordered structure A1 and icosahedral habit.