Layering misalignment and negative temperature dependence of interfacial free energy of B2-liquid interfaces in a glass forming system

From molecular dynamics simulations and the capillary fluctuation method, the solid-liquid interfacial free energy ( γ 0 ) has been computed for the B2-liquid interface in the Cu-Zr system. Consistent with previous results for the FCC-liquid interface in Cu-Zr and Al-Sm but atypical of most alloys, γ 0 was found to increase as the temperature is lowered. In addition, the temperature dependence was obtained for model Lennard-Jones B2-liquid alloys. In all cases the unusual temperature dependence of γ 0 is correlated with an atomic structure of the interfacial region characterized by a misalignment of the number density peaks between solvents and solutes. In cases where the number density peaks are aligned, the typical temperature dependence is observed. The results are discussed in terms of the Gibbs theory of the thermodynamics of interfaces. It is proposed that the unique interfacial structure and the atypical temperature dependence of γ 0 are hallmarks of an easy glass forming alloy.