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).

Program summary

Program title: cij

CPC Library link to program files: https://doi.org/10.17632/b8xf5jh5s8.1

Developer's repository link: https://github.com/MineralsCloud/cij

Licensing provisions: GNU General Public License 3

Programming language: Python 3

Nature of problem: Experimental measurements of full elastic tensor coefficients under high-pressure and high-temperature conditions are challenging and susceptible to uncertainties. Computations of thermoelastic coefficients based on the conventional density functional theory (DFT) plus quasiharmonic approximation (QHA) or ab initio molecular dynamics (AIMD) methods are computationally extremely demanding, especially for materials with low symmetries because of the revaluation of free energy for strained configurations.

Solution method: Based on a semi-analytical method proposed by Wu and Wentzcovitch [1], we developed a handy code that only needs static-state elastic coefficients and phonon vibrational density of states for several equilibrium configurations at different pressure points as input to calculate the thermal elasticity. This method avoids the reevaluation of free energy for strained configurations and can be applied to all crystal systems.

Reference

[1]

Z. Wu, R.M. Wentzcovitch, Phys. Rev. B 83 (2011) 184115.

中文翻译：

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cij：准谐波热弹性的 Python 代码

Wu-Wentzcovitch 半解析法 (SAM) 是一种计算结晶材料的高压高温 (high- PT ) 热弹性张量 (Cij) 的简洁预测形式。该方法已成功应用于不同晶体系统的材料，并结合静态弹性系数和声子频率的从头计算。这些结果提供了对地幔成分和结构的第一手资料。

这里我们介绍cij包，它是 SAM-Cij 形式主义的 Python 实现。它使热弹性计算能够从单个命令启动，并且可以从计算设置文件中完全配置，以处理任何结晶系统中的固体。这些功能允许 SAM-Cij 计算在个人计算机上工作，并作为高通量工作流程的一部分轻松集成。在这里，我们展示了该代码对来自不同晶体系统的三种矿物在其相关PT s 上的性能：透辉石（单斜晶）、秋元石（三角晶）和桥晶石（斜方晶）。

程序概要

节目名称： cij

CPC 库程序文件链接： https : //doi.org/10.17632/b8xf5jh5s8.1

开发者仓库链接： https : //github.com/MineralsCloud/cij

许可条款：GNU 通用公共许可证 3

编程语言： Python 3

问题性质：在高压和高温条件下对全弹性张量系数进行实验测量具有挑战性并且容易受到不确定性的影响。基于传统密度泛函理论 (DFT) 加拟调和近似 (QHA) 或从头分子动力学 (AIMD) 方法计算热弹性系数在计算上要求极高，特别是对于具有低对称性的材料，因为应变构型的自由能重估.

求解方法：基于 Wu 和 Wentzcovitch [1] 提出的半解析方法，我们开发了一个方便的代码，只需将不同压力点下几种平衡配置的静态弹性系数和声子振动状态密度作为输入来计算热弹性。这种方法避免了重新评估应变构型的自由能，并且可以应用于所有晶体系统。

参考

[1]

Z. Wu，RM Wentzcovitch，物理。修订版 B 83 (2011) 184115。