On glass formation thermodynamics: Enthalpy vs. Entropy

Abstract

Glass formation thermodynamics usually concerns the liquid-crystal Gibbs free energy difference. But, in practice, its efficiency in predicting the occurrence of the glass transition of materials and guiding the composition design is quite quantitative. In particular, it remains to be clarified to understand the relationship between and the contributions to the two fundamental quantities of enthalpy and entropy involved herein. In this paper, we study the relation between the enthalpy and the entropy involved in glass formation of various materials, and find that they are strongly correlated with each other. Theoretical and experimental analyses indicate the intrinsic correlation of the entropy of fusion with other key parameters associated with glass formation like melting viscosity and enthalpy of mixing, which confirms the close relation between the entropy of fusion and glass formation. Close inspection finds that the low entropy of fusion benefits the glass formation. Owing to the fact that the two glass-formation key variables of viscosity and enthalpy can be addressed by the entropy of fusion, we propose that the entropy of fusion be able to serve as a representative thermodynamic quantity to understand the glass formation in materials. The reliability in understanding the glass formation in terms of entropy of fusion is further verified. The studies provide a new reference for developing the glass formation thermodynamics.