Npj Comput. Mater.: 高热电性能—全赫斯勒化合物

海归学者发起的公益学术平台

分享信息，整合资源

交流学术，偶尔风月

来自烟台大学物理与电子信息学院的戴振宏教授团队联合清华大学倪军教授团队和中科院物理所孟胜研究员团队，采用先进的第一性原理计算方法，该方法能够考虑四阶非谐性对声子输运性质的影响和完整的电声耦合机制，以预测全赫斯勒化合物Na₂TlSb晶格热导率和热电品质因数。

Fig. 2 Phonon transport properties.

该研究发现Na₂TlSb的超低的晶格热导率可以用小的声子群速度和强的三声子和四声子散射来解释。此外，具有rattling行为的Tl原子具有很强的温度依赖性和三次和四次非谐性，在晶格动力学稳定性中起着重要的作用。

Fig. 3 Phonon transport parameter

Na₂TlSb中的低频四声子散射率可以比拟甚至超过三声子散射率。强的声子高阶非谐性和小的声子群速度是软的Tl-Sb键和在由Na和Sb原子之间的组成的赝笼中的共振键结合的作用。

Fig. 4 Phonon scattering.

同时，价带顶处的多谷带结构增加了带的简并度，导致p型Na₂TlSb具有较高的热电功率因数。此外，由于在导带底处的大电子带色散和显著的带不对称性，导致n型Na₂TlSb高的电导率，从而导致好的电子性质。低的晶格热导率和高功率因子的结合表明Na₂TlSb具有广阔的热电应用前景。

Fig. 5 Electron structure.

该研究有助于理解具有强四次非谐性的全赫斯勒化合物的超低κ_L的起源，从而合理设计具有高热电性能的全赫斯勒化合物。该文近期发表于npj Computational Materials 9,: 17(2023)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Strong quartic anharmonicity, ultralow thermal conductivity,

high band degeneracy and good thermoelectric performance in Na2TlSb

Tongcai Yue, Yinchang Zhao, Jun Ni, Sheng Meng & Zhenhong Dai

We employ first-principles calculations combined with self-consistent phonon theory and Boltzmann transport equations to investigate the thermal transport and thermoelectric properties of full-Heusler compound Na2TlSb. Our findings exhibit that the strong quartic anharmonicity and temperature dependence of the Tl atom with rattling behavior plays an important role in the lattice stability of Na2TlSb. We find that soft Tl-Sb bonding and resonant bonding in the pseudocage composed of the Na and Sb atoms interaction is responsible for ultralow κL. Meanwhile, the multi-valley band structure increases the band degeneracy, results in a high power factor in p-type Na2TlSb. The coexistence of ultralow κL and high power factor presents that Na2TlSb is a potential candidate for thermoelectric applications. Moreover, these findings help to understand the origin of ultralow κL of full-Heusler compounds with strong quartic anharmonicity, leading to the rational design of full-Heusler compounds with high thermoelectric performance.