钯、铂、铜和金的第一性原理准谐热弹性
Quasi-harmonic thermoelasticity of palladium, platinum, copper, and gold from first principles
摘要：
我们计算钯，铂，铜和金的温度依赖性的弹性常数的准谐波近似内使用第一性原理的方法和数值评估的亥姆霍兹自由能的二阶导数相对于应变在最小的自由能本身。我们发现一个整体良好的协议与实验数据，虽然钯和铂在室温下报告的异常没有再现。电子激发的贡献也进行了研究：我们发现，它是不可忽略的$C_{44}$弹性常数的钯和铂，而它是无关紧要的在其他情况下。它的影响不足以解释实验发现的异常的细节，即使在铂的情况下，我们考虑到电子-声子相互作用。最后，交换和相关功能的效果得到解决，它被发现，这是重要的，在T=0 K，而所有的泛函给出类似的温度依赖性。
英文摘要：
We calculate the temperature-dependent elastic constants of palladium, platinum, copper and gold within the quasi-harmonic approximation using a first-principles approach and evaluating numerically the second derivatives of the Helmholtz free-energy with respect to strain at the minimum of the free-energy itself. We find an overall good agreement with the experimental data although the anomalies of palladium and platinum reported at room temperature are not reproduced. The contribution of electronic excitations is also investigated: we find that it is non-negligible for the $C_{44}$ elastic constants of palladium and platinum while it is irrelevant in the other cases. Its effect is not sufficient to explain the details of the anomalies found by experiments, not even when, in the case of platinum, we take into account the electron-phonon interaction. Lastly, the effect of the exchange and correlation functional is addressed and it is found that it is important at T=0 K, while all functionals give similar temperature dependencies.
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