Zhou Yu, Zhao Ying-Qin, Zeng Zhao-Yi, Chen Xiang-Rong, Geng Hua-Yun
College of Physics, Sichuan University, Chengdu 610065, China.
College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400047, China.
Phys Chem Chem Phys. 2019 Jul 10;21(27):15167-15176. doi: 10.1039/c9cp02020a.
Weyl semimetal, a newly developed thermoelectric material, has aroused much interest due to its extraordinary transport properties. In this work, the thermoelectric transport properties of NbX (X = P and As), a prototypical Weyl semimetal, are investigated using the first-principles calculations together with Boltzmann transport theory. The calculated room-temperature lattice thermal conductivities along the a and c directions are 2.0 W mK-1 and 0.6 W mK-1 for NbP and 1.4 W mK-1 and 0.4 W mK-1 for NbAs, respectively. The low thermal conductivities may be useful in the thermoelectric applications. It is found that the acoustic branches have obvious contribution to the total lattice thermal conductivity, and the size dependence of the thermal conductivities can provide guidance for designing thermoelectric nanostructures. Our results show that the anisotropic structures of these compounds bring about the anisotropy of transport coefficients along the a and c directions, and the preferred direction is the c direction in thermoelectric applications. Moreover, NbP and NbAs show high ZT values of 0.82 and 0.50 along the c direction for p-type at an optimal carrier concentration, indicating that they are potential thermoelectric materials.
外尔半金属是一种新开发的热电材料，因其非凡的输运特性而引起了广泛关注。在这项工作中，使用第一性原理计算结合玻尔兹曼输运理论研究了典型外尔半金属NbX（X = P和As）的热电输运特性。对于NbP，沿a方向和c方向计算得到的室温晶格热导率分别为2.0 W mK-1和0.6 W mK-1，对于NbAs则分别为1.4 W mK-1和0.4 W mK-1。低的热导率在热电应用中可能是有用的。发现声学支对总晶格热导率有明显贡献，并且热导率的尺寸依赖性可为设计热电纳米结构提供指导。我们的结果表明，这些化合物的各向异性结构导致了沿a方向和c方向输运系数的各向异性，并且在热电应用中优选方向是c方向。此外，在最佳载流子浓度下，NbP和NbAs沿c方向对于p型显示出0.82和0.50的高ZT值，表明它们是潜在的热电材料。
