Thermodynamic determination of fragility in La-based glass-forming liquid

Differences in the thermodynamic functions between the liquid and crystalline states of La-based bulk metallic glasses alloys were calculated with the specific heat capacity C _p and the fusion heat ΔH _f, which we measured. Fragility indexes having different thermodynamic definitions were calculated from the temperature dependence of excess entropy ΔS ^liq-cry. It is ambiguous for La-based glass-forming liquid to evaluate fragility from the intercepts of ΔSliq-cry-temperature curves. We found that the thermodynamic fragility M _ΔS , denoted ΔS, decreases at the onset melting temperatures T _m rather than at glass transition temperatures T _g, and relates linearly with the kinetic fragility m. The correlations between thermodynamic fragility and kinetic fragility are discussed within the frameworks of the Adam-Gibbs relationship and potential energy landscape theory.