Prediction on temperature dependent elastic constants of "soft" metal Al by AIMD and QHA
Prediction on temperature dependent elastic constants of "soft" metal Al by AIMD and QHA
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通过 AIMD 和 QHA 预测“软”金属 Al 的温度相关弹性常数
DOI：
10.1016/j.jmst.2019.11.029
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发表时间：
2020
影响因子：
10.9
通讯作者：
Hu Qingmiao
中科院分区：
文献类型：
--
作者：
Zhang Haijun;Li Chenhui;Djemia Philippe;Yang Rui;Hu Qingmiao
基于密度泛函理论（DFT）的第一性原理方法现在通常用于计算材料在0 K温度下的弹性常数。然而，有限温度下弹性常数的第一性原理计算并不简单。本文以面心立方（FCC）铝（Al）为例，探讨了从头计算分子动力学（AIMD）方法在计算相对“软”金属的温度依赖弹性常数中的可行性。使用精心选择的应变张量和应变幅度进行AIMD计算。在进行有源植入式医疗器械计算的同时，还进行了准谐波近似（QHA）的第一性原理计算。我们发现，所有三个独立的弹性常数分量（C11，C12和C44）的AIMD和QHA计算的Al随温度T的增加而减少，在良好的协议与实验测量。我们的工作使我们能够量化的体积膨胀，晶格振动（不包括那些有助于体积膨胀），和电子温度效应的温度引起的弹性常数的变化的个人贡献。对于具有稳定面心立方晶体结构的Al，体积膨胀效应对弹性常数的温度变化贡献最大（约75%~ 80%）。晶格振动的贡献很小（约20%-25%），而电子温度效应可以忽略不计。虽然弹性常数软化随着温度的升高，FCC铝满足玻恩弹性稳定性标准的温度高达实验熔点。
First-principles methods based on density functional theory (DFT) are nowadays routinely applied to calculate the elastic constants of materials at temperature of 0 K. Nevertheless, the first-principles calculations of elastic constants at finite temperature are not straightforward. In the present work, the feasibility of the ab initio molecular dynamic (AIMD) method in calculations of the temperature dependent elastic constants of relatively “soft” metals, taking face centered cubic (FCC) aluminum (Al) as example, is explored. The AIMD calculations are performed with carefully selected strain tensors and strain magnitude. In parallel with the AIMD calculations, first-principles calculations with the quasiharmonic approximation (QHA) are performed as well. We show that all three independent elastic constant components (C11,C12andC44) of Al from both the AIMD and QHA calculations decrease with increasing temperatureT, in good agreement with those from experimental measurements. Our work allows us to quantify the individual contributions of the volume expansion, lattice vibration (excluding those contributed to the volume expansion), and electronic temperature effects to the temperature induced variation of the elastic constants. For Al with stable FCC crystal structure, the volume expansion effect contributes the major part (about 75%∼80%) in the temperature induced variation of the elastic constants. The contribution of the lattice vibration is minor (about 20%∼25%) while the electronic temperature effect is negligible. Although the elastic constants soften with increasing temperature, FCC Al satisfies the Born elastic stability criteria with temperature up to the experimental melting point.