A self-consistent approach to describe unit-cell-parameter and volume variations with pressure and temperature

Ross Angel; Mattia Mazzucchelli; Javier Gonzalez-Platas; Matteo Alvaro

doi:10.1107/S1600576721009092

A self-consistent approach to describe unit-cell-parameter and volume variations with pressure and temperature

J Appl Crystallogr. 2021 Oct 27;54(Pt 6):1621-1630. doi: 10.1107/S1600576721009092. eCollection 2021 Dec 1.

Authors

Ross Angel¹, Mattia Mazzucchelli², Javier Gonzalez-Platas³, Matteo Alvaro⁴

Affiliations

¹ IGG, CNR, Via G. Gradenigo, 6, Padova, Padova I-35131, Italy.
² Mainz Institute of Multiscale Modeling and Institute of Geosciences, Johannes-Gutenberg University of Mainz, J.-J.-Becher-Weg 21, Mainz D-55128, Germany.
³ Departamento de Física, Instituto Universitario de Estudios Avanzados en Física Atómica, Molecular y Fotónica (IUDEA), MALTA Consolider Team, Universidad de La Laguna, La Laguna, Tenerife E-38204, Spain.
⁴ Department of Earth and Environmental Sciences, University of Pavia, Via A. Ferrata 1, Pavia I-27100, Italy.

Abstract

A method for the self-consistent description of the large variations of unit-cell parameters of crystals with pressure and temperature is presented. It employs linearized versions of equations of state (EoSs) together with constraints to ensure internal consistency. The use of polynomial functions to describe the variation of the unit-cell angles in monoclinic and triclinic crystals is compared with the method of deriving them from linearized EoSs for d spacings. The methods have been implemented in the CrysFML Fortran subroutine library. The unit-cell parameters and the compressibility and thermal expansion tensors of crystals can be calculated from the linearized EoSs in an internally consistent manner in a new utility in the EosFit7c program, which is available as freeware at http://www.rossangel.net.

Keywords: EosFit; equations of state; pressure; unit-cell parameters.

Grants and funding

This work was funded by H2020 European Research Council grant 714936 to Matteo Alvaro; Alexander von Humboldt-Stiftung; Agencia Estatal de Investigación grant PID2019-106383GB-C44/AEI/10.13059/501100011033 to Javier Gonzalez-Platas; Ministero dell’Istruzione, dell’Università e della Ricerca grant 2017ZE49E7.