Model predicts the entropy of melting

Thermal energy storage based on the melting of materials have many current and potential applications, such as the heating and cooling of buildings and the thermal management of devices, like batteries and electronics. Lilley et al. develop a model predicting the entropy of melting rather than determining it from experimental data and/or empirical rules.

The researchers used simple arguments about an atom’s motion in liquids to understand why the amount of entropy it takes to melt or vaporize metals hovers around a nominal value.

“A model that can explain the entropy change at melting can be directly used to design such materials, because the heat absorbed or released on melting -- or the enthalpy change -- is directly proportional to the entropy change,” said author Ravi Prasher.

While prior models can predict the relative change in entropy or heat capacity within the liquid state quite well, the absolute value is needed to predict phase equilibria and entropy of fusion. The researchers used common material parameters to determine the absolute value of thermodynamic properties in the liquid state.

“This model could be useful in predicting performance of new materials in the absence of extensive experimental thermodynamic data, especially in applications requiring multi-phase thermodynamic cycles, such as refrigeration, heat exchange and thermal storage,” said Prasher.

To build on their work creating a simple analytical model to predict thermodynamic properties of monatomic liquids, future work will focus on the effects of intra-molecular interactions to test the model for multiatomic systems.

Source: “A simple model for the entropy of melting of monatomic liquids,” by Drew Lilley, Anubhav Jain, and Ravi Prasher, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0041604 .