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

• Published in: npj computational materials 2018-07, Vol.4 (1), p.1-7, Article 40
• Main Authors: Latimer, Katherine, Dwaraknath, Shyam, Mathew, Kiran, Winston, Donald, Persson, Kristin A.
• Format: Article
• Language: English
• Subjects: 639/301/1034/1035; 639/301/1034/1037; Bulk modulus; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computational Intelligence; Energy storage; Entropy; Equations of state; Geophysics; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; Mathematical analysis; Mathematical and Computational Engineering; Mathematical and Computational Physics; Mathematical Modeling and Industrial Mathematics; Mathematical models; Organic chemistry; Theoretical
• ISSN: 2057-3960; 2057-3960
• DOI: 10.1038/s41524-018-0091-x

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. Equations of State: which are best? A systematic comparison between the performances of several thermodynamic equations of state revealed the superiority of three equations. Equations of state are widely used to describe materials properties based on variables like temperature, pressure, volume, etc. Now, a team from University of California Berkeley and the Lawrence Berkeley National Lab aim to determine the most suitable one for various conditions. The authors used DFT calculations to model the properties of hundreds of elemental, binary and ternary crystalline solids and subsequently fit them with the most commonly-used equations of state. The Birch, Tait and Vinet equations showed the lowest deviation from calculated points, while fitting reasonably well experimental data; this holistic approach underlines that there is not one equation of state to fit all cases.