Q-POP-Thermo: A general-purpose thermodynamics solver for ferroelectric materials

Q-POP-Thermo is a program designed to compute thermodynamic monodomain equilibrium states and their properties for ferroelectric single crystals and thin films based on the Landau-Ginzburg-Devonshire (LGD) Theory. Utilizing symbolic manipulation with the SymPy Library, the governing equations along with appropriate boundary conditions are solved for speedy minimization of the free energy of a crystal. Utilizing the popular Differential Evolution algorithm, with appropriate hybridization, multiple phase diagrams, such as the pressure-temperature phase diagram for bulk single crystals and the common strain-temperature phase diagram for monodomain thin-film systems can be readily generated. Furthermore, a variety of material properties of stable ferroelectric phases, including dielectric, piezoelectric, and electrocaloric properties, can simultaneously be calculated. Validation studies are presented for both thin-film and single crystal systems to test the effectiveness and capability of the open-source program. Program summary: Program title: Q-POP-Thermo CPC Library link to program files: https://doi.org/10.17632/wd6228g9ww.1 Code Ocean capsule: https://codeocean.com/capsule/1245708 Licensing provisions: MIT Programming language: Python External routines/libraries: numpy (Version 1.20.3), sympy (Version 1.8), numerical optimization (available with Q-POP-Thermo), pandas (Version 1.1.3), scipy (Version 1.6.3) Nature of program: Python-based program to perform energy minimization to determine the stable states and thermodynamic properties of ferroelectric systems. Solution method: Algebraic manipulation of boundary conditions and governing equations followed by a hybridized and improved a priori Differential Evolution solver to calculate equilibrium polar states and material properties.