Violation of the T -1 Relationship in the Lattice Thermal Conductivity of Mg3Sb2 with Locally Asymmetric Vibrations

Yifan Zhu; Yi Xia; Yancheng Wang; Ye Sheng; Jiong Yang; Chenguang Fu; Airan Li; Tiejun Zhu; Jun Luo; Christopher Wolverton; G Jeffrey Snyder; Jianjun Liu; Wenqing Zhang

doi:10.34133/2020/4589786

Violation of the T ^-1 Relationship in the Lattice Thermal Conductivity of Mg₃Sb₂ with Locally Asymmetric Vibrations

Research (Wash D C). 2020 Nov 30:2020:4589786. doi: 10.34133/2020/4589786. eCollection 2020.

Authors

Yifan Zhu^{1

2

3}, Yi Xia⁴, Yancheng Wang^{1

2}, Ye Sheng³, Jiong Yang^{1

3}, Chenguang Fu⁵, Airan Li⁶, Tiejun Zhu⁶, Jun Luo^{3

7}, Christopher Wolverton⁴, G Jeffrey Snyder⁴, Jianjun Liu^{1

2}, Wenqing Zhang^{1

8

9}

Affiliations

¹ State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Materials Genome Institute, Shanghai University, Shanghai 200444, China.
⁴ Department of Materials Science and Engineering, Northwestern University, IL 60208, USA.
⁵ Max Planck Institute for Chemical Physics of Solids, Dresden 01187, Germany.
⁶ State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
⁷ School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China.
⁸ Department of Physics and Shenzhen Institute for Quantum Science & Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
⁹ Guangdong Provincial Key Lab for Computational Science and Materials Design and Shenzhen Municipal Key Lab for Advanced Quantum Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China.

Abstract

Most crystalline materials follow the guidelines of T ^-1 temperature-dependent lattice thermal conductivity (κ _L ) at elevated temperatures. Here, we observe a weak temperature dependence of κ _L in Mg₃Sb₂, T ^-0.48 from theory and T ^-0.57 from measurements, based on a comprehensive study combining ab initio molecular dynamics calculations and experimental measurements on single crystal Mg₃Sb₂. These results can be understood in terms of the so-called "phonon renormalization" effects due to the strong temperature dependence of the interatomic force constants (IFCs). The increasing temperature leads to the frequency upshifting for those low-frequency phonons dominating heat transport, and more importantly, the phonon-phonon interactions are weakened. In-depth analysis reveals that the phenomenon is closely related to the temperature-induced asymmetric movements of Mg atoms within MgSb₄ tetrahedron. With increasing temperature, these Mg atoms tend to locate at the areas with relatively low force in the force profile, leading to reduced effective 3^rd-order IFCs. The locally asymmetrical atomic movements at elevated temperatures can be further treated as an indicator of temperature-induced variations of IFCs and thus relatively strong phonon renormalization. The present work sheds light on the fundamental origins of anomalous temperature dependence of κ _L in thermoelectrics.