Short-range and medium-range order in supercooled liquids of alloys

Relaxation behavior of structural change at the atomic cluster level in supercooled liquids during isothermal annealing processes is investigated for a model alloy system by using molecular dynamics simulations. The simulation results show that the short-range icosahedral order grows with the annealing time. Moreover, the spatial distribution of the icosahedral clusters shows a medium-range order of a few nanometers. This type of geometrical short-range order of icosahedral symmetry is drastically enhanced by alloying components with a large atomic size difference and negative heat of mixing. On the other hand, various types of chemical short-range order grow according to a combination of heats of mixing.