Unusual temperature dependence of the solid-liquid interfacial free energy in the Cu-Zr system

The solid-liquid portion of the equilibrium phase diagram at the Cu rich side of a Finnis-Sinclair description of Cu-Zr was determined by a combination of molecular dynamics and semi-grand canonical Monte Carlo simulations and the model system was found to be in very good agreement with experiment. Molecular dynamics simulations and the capillary fluctuation method were used to compute the solid-liquid interfacial free energy, γ , and its anisotropy as a function of undercooling. Unlike the case of pure metals and in contrast to most previous atomistic studies in alloy systems, γ was found to increase with decreasing temperature and the increase is quite pronounced. To verify the unusual results, the excess energy and number of Zr atoms were computed for the [1 0 0] interface and from the excess thermodynamic quantities γ was obtained through a thermodynamic integration. The results of the two approaches for computing γ are in agreement to within the statistical uncertainties. The implications of the temperature behavior of γ is discussed in terms of crystal nucleation from the melt and glass formation.