EosFit7c and a Fortran module (library) for equation of state calculations

• Published in: Zeitschrift für Kristallographie. Crystalline materials Vol. 229; no. 5; pp. 405 - 419
• Main Authors: Angel, Ross J., Alvaro, Matteo, Gonzalez-Platas, Javier
• Format: Journal Article
• Language: English
• Published: München De Gruyter Oldenbourg 01.01.2014; Oldenbourg
• Subjects: Condensed matter: structure, mechanical and thermal properties; EosFit; equations of state; Equations of state of specific substances; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Mechanical and acoustical properties; Physical properties of thin films, nonelectronic; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); thermal expansion; Thermal expansion; thermomechanical effects and density; Thermal properties of condensed matter; Thermal properties of crystalline solids; Thermal expansion; Reviews; Equations of state; Computer software; EosFit; Mechanical properties; Elasticity theory; Ab initio calculations; Least square fit; Thermal model
• ISSN: 2194-4946; 2196-7105
• DOI: 10.1515/zkri-2013-1711

The relationship between linear elasticity theory of solids and their equations of state (EoS) is reviewed, along with the commonly-used types of isothermal EoS, thermal expansion models, and P-V-T EoS. A new console program, EosFit7c, is presented. It performs EoS calculations and fitting for both volume and linear isothermal data, isobaric data and P-T data. Linear data is handled by cubing the quantities and treating them as volumes in all EoS formulations. Least-squares fitting of EoS to data incorporates the option to weight the fit with the measurement uncertainties in P, V and T simultaneously. The EosFit7c program is built with a new library of subroutines for EoS calculations and manipulation, written in Fortran. The library has been incorporated as a module, cfml_eos, in the publicly-available CrysFML library. The module handles Murnaghan, Tait, Birch-Murnaghan, Vinet, and Natural Strain EoS. For P-V-T calculations any of these isothermal EoS can be combined with a variety of published thermal expansion models, including a model of thermal pressure. The entire library has been revalidated against other software and against an ab-initio re-derivation of the EoS, which identified a number of small errors in published formulae for some EoS.