Accordance of glass formation criteria: Entropic vs structural

Abstract

Increasing evidences show the significance of low melting entropy in glass formation of substances. Our previous studies have uncovered the strong dependence between melting entropy in the eutectic mixtures and mixing enthalpy, which has been serving as an important reference for glass formation, showing that negative mixing enthalpy largely reduces the melting entropy. In this paper, we focused on the question as to how melting entropy is associated with another classical glass formation criterion of molecule/atom size difference of components. This question has been challenging since it is constantly entangled with the effect of mixing enthalpy and easily smeared. Here, four binary eutectics constituted by molecules with similar structural and chemical characteristics but quite different molecular size were elaborately selected. The extremely low mixing enthalpy measured in four eutectic systems using a C80 microcalorimeter guarantees the neglectable effect of the mixing enthalpy. The determination of melting entropies and the critical cooling rate for glass formation at the eutectic compositions for the four systems uncovers an evident relation between melting entropy and molecular size difference, confirming the compatibility of the two glass formation criteria for mixing systems.