cij: A Python code for quasiharmonic thermoelasticity

The Wu-Wentzcovitch semi-analytical method (SAM) is a concise and predictive formalism to calculate the high-pressure and high-temperature (high-PT) thermoelastic tensor (Cij) of crystalline materials. This method has been successfully applied to materials across different crystal systems in conjunction with ab initio calculations of static elastic coefficients and phonon frequencies. Such results have offered first-hand insights into the composition and structure of the Earth's mantle.

Here we introduce the cij package, a Python implementation of the SAM-Cij formalism. It enables a thermoelasticity calculation to be initiated from a single command and fully configurable from a calculation settings file to work with solids within any crystalline system. These features allow SAM-Cij calculations to work on a personal computer and to be easily integrated as a part of high-throughput workflows. Here we show the performance of this code for three minerals from different crystal systems at their relevant PTs: diopside (monoclinic), akimotoite (trigonal), and bridgmanite (orthorhombic).

Wu-Wentzcovitch半解析方法（Semi-analytical Method，SAM）是一种简洁且具备预测性的形式化方法，用于计算晶体材料的高压高温（high-PT）热弹性张量（Cij）。该方法已结合静态弹性系数与声子频率的从头算（ab initio）计算，成功应用于不同晶系的材料。相关研究结果为地球地幔的组成与结构提供了第一手的认知参考。
本文介绍了cij包——一种SAM-Cij形式化方法的Python实现。该工具可通过单条命令启动热弹性计算，并可通过计算配置文件完成全参数配置，支持任意晶系的固体材料计算。这些特性使得SAM-Cij计算可在个人计算机上运行，且可轻松集成至高通量工作流中。本文展示了该代码在三种不同晶系矿物的相关PT条件下的计算性能：透辉石（单斜晶系）、秋田石（三方晶系）以及布里奇曼石（斜方晶系）。