First-principles calculations and experimental studies of XYZ(2) thermoelectric compounds: detailed analysis of van der Waals interactions
First-principles calculations and experimental studies of XYZ(2) thermoelectric compounds: detailed analysis of van der Waals interactions
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XYZ(2)热电化合物的第一性原理计算和实验研究：范德华相互作用的详细分析
DOI：
10.1039/c8ta06470a
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发表时间：
2018
影响因子：
11.9
通讯作者：
White Mary Anne
中科院分区：
文献类型：
--
作者：
Pohls Jan Hendrik;Luo Zhe;Aydemir Umut;Sun Jon Paul;Hao Shiqiang;He Jiangang;Hill Ian G;Hautier Geoffroy;Jain Anubhav;Zeng Xiaoqin;Wolverton Chris;Snyder G Jeffrey;Zhu Hong;White Mary Anne
第一性原理计算可以加速寻找新的高性能热电材料。然而，热电性能的预测强烈依赖于用于计算的近似。在此，用不同的计算近似（即，PBE-GGA，HSE 06，自旋-轨道耦合和DFT-D3）的三层XYZ 2化合物（TmAgTe 2，YAgTe 2和YCuTe 2）。除了计算，这些化合物的结构，电学和热学性质进行了实验测量，并与计算结果进行了比较。通过引入货车德瓦耳斯相互作用，可以更准确地模拟原子间的作用力，从而提高了对晶体结构和热容的预测。特别地，从色散优化结构观察到声学声子和低频光学声子向较低频率的大位移。从这些化合物的声子色散曲线，在所研究的XYZ 2化合物的超低热导率可以描述由最近开发的最小热导率模型。对于电导率的预测，使用依赖于温度的弛豫时间，并且它受到声学声子的限制。虽然HSE 06由于计算的带隙能量>0.25 eV而对电学性质只有很小的影响，但包含货车范德华相互作用和自旋轨道耦合导致更准确的能带结构，从而更好地预测电学性质。此外，测量了YAgTe 2、TmAg0.95Zn0.05Te2和TmAg0.95Mg0.05Te2的实验热电性能，表明与TmAgTe 2相比，TmAg0.95Zn0.05Te2的zT增加超过35%（zT = 0.47 ± 0.12）。
First-principles calculations can accelerate the search for novel high-performance thermoelectric materials. However, the prediction of the thermoelectric properties is strongly dependent on the approximations used for the calculations. Here, thermoelectric properties were calculated with different computational approximations (i.e., PBE-GGA, HSE06, spin–orbit coupling and DFT-D3) for three layered XYZ2 compounds (TmAgTe2, YAgTe2, and YCuTe2). In addition to the computations, the structural, electrical and thermal properties of these compounds were measured experimentally and compared to the computations. An enhanced prediction of the crystal structure and heat capacity was achieved with the inclusion of van der Waals interactions due to more accurate modeling of the interatomic forces. In particular, a large shift of the acoustic phonons and low-frequency optical phonons to lower frequencies was observed from the dispersion-optimized structure. From the phonon dispersion curves of these compounds, the ultralow thermal conductivity in the investigated XYZ2 compounds could be described by a recent developed minimum thermal conductivity model. For the prediction of the electrical conductivity, a temperature-dependent relaxation time was used, and it was limited by acoustic phonons. While HSE06 has only a small influence on the electrical properties due to a computed band gap energy of >0.25 eV, the inclusion of both van der Waals interactions and spin–orbit coupling leads to a more accurate band structure, resulting in better prediction of electrical properties. Furthermore, the experimental thermoelectric properties of YAgTe2, TmAg0.95Zn0.05Te2 and TmAg0.95Mg0.05Te2 were measured, showing an increase in zT of TmAg0.95Zn0.05Te2 by more than 35% (zT = 0.47 ± 0.12) compared to TmAgTe2.