Low thermal conductivity is favorable for preserving the temperature gradient between the two ends of a thermoelectric material, in order to ensure continuous electron current generation. In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic in PbTe and SnSe, and phonon scattering resulting from the dynamic disorder in AgCrSe2 and CuCrSe2, which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in α-MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the compound's intrinsic distorted rocksalt sublattice, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in α-MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials.

中文翻译：

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变形的晶体α-MgAgSb中横向声子抑制产生的超低热导率。

低的热导率有利于保持热电材料的两端之间的温度梯度，以确保连续的电子电流产生。在高性能热电材料中，主要有两种低热导率机理：PbTe和SnSe中的声子非调和，以及AgCrSe2和CuCrSe2中的动态无序导致的声子散射，这已通过非弹性中子散射成功地揭示出来。使用中子散射和从头算的方法，我们在这里报告了静态局部结构变形与声子-非谐波诱导的α-MgAgSb超低晶格热导率结合的机理。由于横向声子几乎被化合物固有的扭曲岩石盐子晶格完全散射，热量主要通过纵向声子传递。α-MgAgSb的超低热导率归因于其原子动力学因结构畸变而改变，这为增强类似热电材料的性能提供了可能的微观途径。