Evaluation of thermodynamic equations of state across chemistry and structure in the materials project

Katherine Latimer,Donald Winston,Kiran Mathew,Shyam Dwaraknath,Kristin A. Persson

doi:10.1038/s41524-018-0091-x

Abstract

Thermodynamic equations of state (EOS) for crystalline solids describe material behaviors under changes in pressure, volume, entropy and temperature, making them fundamental to scientific research in a wide range of fields including geophysics, energy storage and development of novel materials. Despite over a century of theoretical development and experimental testing of energy–volume (E–V) EOS for solids, there is still a lack of consensus with regard to which equation is indeed optimal, as well as to what metric is most appropriate for making this judgment. In this study, several metrics were used to evaluate quality of fit for 8 different EOS across 87 elements and over 100 compounds which appear in the literature. Our findings do not indicate a clear “best” EOS, but we identify three which consistently perform well relative to the rest of the set. Furthermore, we find that for the aggregate data set, the RMSrD is not strongly correlated with the nature of the compound, e.g., whether it is a metal, insulator, or semiconductor, nor the bulk modulus for any of the EOS, indicating that a single equation can be used across a broad range of classes of materials.

Highlights

Thermodynamic equations of state (EOS) for crystalline solids describe material behaviors under changes in pressure, volume, entropy and temperature; making them fundamental to scientific research in a wide range of fields, including geophysics, energy storage and development of novel materials.[1,2,3] Despite over a century of theoretical development and experimental testing of EOS for solids,[4,5] there is still a lack of consensus on the most appropriate EOS under various conditions or even the metric to evaluate appropriateness
These considerations pave the way for high-throughput studies that probe extreme conditions using Density-functional theory (DFT) generated EOS
Both forms of the Birch equation were derived by Francis Birch in 1947 for crystalline solids of cubic symmetry.[10]

Summary

Introduction

Thermodynamic equations of state (EOS) for crystalline solids describe material behaviors under changes in pressure, volume, entropy and temperature; making them fundamental to scientific research in a wide range of fields, including geophysics, energy storage and development of novel materials.[1,2,3] Despite over a century of theoretical development and experimental testing of EOS for solids,[4,5] there is still a lack of consensus on the most appropriate EOS under various conditions or even the metric to evaluate appropriateness. The RMSrD values for the fits of all EOS across the investigated material set are shown for the elements (Fig. 1) (see Supplementary Fig. S1 in SI for data on the compound set).

Results

Conclusion