In this paper, we report a theoretical study of the structural, electronic, thermoelectric and piezoelectric properties of TaXSn (X = Co, Rh and Ir) half-Heusler compounds crystallizing with cubic MgAgAs-type structure. We have made a quantitative evaluation of thermoelectric figure of merit (ZT) and the electromechanical coupling coefficient (k14) of these compounds. Accordingly, we intend to combine the first-principles band structure calculations using (DFT)-based FP-LAPW approach and the semi-classical Boltzmann transport theory within constant scattering time approximation (CSTA) to interpret and predict the thermoelectric performance (ZTe) without the lattice thermal conductivity as a function of the chemical potential at various temperatures. Further, to obtain a reasonable estimate for (ZT) with the intrinsic lattice thermal conductivity, we have calculated the relaxation time (τ) at various temperatures using Bardeen–Shockley theory. Finally, for predicting piezoelectric coefficients, we have employed the modern theory of polarization as provided by density-functional perturbation theory (DFPT) based on plane waves and pseudo-potentials (PP-PW). Our key result is that these half-Heusler semiconductors are attractive for practical applications in energy-harvesting technology, which has a high (ZT) and (k14) of 0.89 and 0.25, respectively, at room temperature.

中文翻译：

---

基于 Ab Initio 计算的半赫斯勒化合物 TaXSn（X = Co、Rh 和 Ir）的热电和压电特性

在本文中，我们报告了对具有立方 MgAgAs 型结构结晶的 TaXSn（X = Co、Rh 和 Ir）半赫斯勒化合物的结构、电子、热电和压电特性的理论研究。我们对这些化合物的热电品质因数 (ZT) 和机电耦合系数 (k14) 进行了定量评估。因此，我们打算结合使用基于 (DFT) 的 FP-LAPW 方法的第一性原理能带结构计算和恒定散射时间近似 (CSTA) 内的半经典玻尔兹曼输运理论来解释和预测热电性能 (ZTe)，而无需晶格热导率作为不同温度下化学势的函数。此外，为了获得具有固有晶格热导率的 (ZT) 的合理估计值，我们已经使用 Bardeen-Shockley 理论计算了不同温度下的弛豫时间 (τ)。最后，为了预测压电系数，我们采用了基于平面波和赝势 (PP-PW) 的密度泛函微扰理论 (DFPT) 提供的现代极化理论。我们的主要结果是，这些半赫斯勒半导体对能量收集技术的实际应用很有吸引力，在室温下其 (ZT) 和 (k14) 分别为 0.89 和 0.25。