Yuan Jiaoyue, Chen Yubi, Liao Bolin
Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, USA.
Department of Physics, University of California, Santa Barbara, California 93106, USA.
J Am Chem Soc. 2023 Aug 23;145(33):18506-18515. doi: 10.1021/jacs.3c05091. Epub 2023 Aug 11.
Achieving high thermoelectric performance requires efficient manipulation of thermal conductivity and a fundamental understanding of the microscopic mechanisms of phonon transport in crystalline solids. One of the major challenges in thermal transport is achieving ultralow lattice thermal conductivity. In this study, we use the anti-bonding character of the highest-occupied valence band as an efficient descriptor for discovering new materials with an ultralow thermal conductivity. We first examined the relationship between anti-bonding valence bands (ABVBs) and low lattice thermal conductivity in model systems PbTe and CsPbBr. Then, we conducted a high-throughput search in the Materials Project database and identified over 600 experimentally stable binary semiconductors with an anti-bonding character in their valence bands. From our candidate list, we conducted a comprehensive analysis of the chemical bonds and the thermal transport in the XS family, where X = K, Rb, and Cs are alkaline metals. These materials all exhibit ultralow thermal conductivities less than 1 W/(m K) at room temperature despite simple structures. We attributed the ultralow thermal conductivity to the weakened bonds and increased phonon anharmonicity due to their ABVBs. Our results provide chemical intuitions to understand lattice dynamics in crystals and open up a convenient venue toward searching for materials with an intrinsically low lattice thermal conductivity.
要实现高热电性能，需要有效地控制热导率，并深入理解晶体固体中声子输运的微观机制。热输运中的一个主要挑战是实现超低的晶格热导率。在本研究中，我们利用最高占据价带的反键特性作为一种有效的描述符，来发现具有超低热导率的新材料。我们首先在模型体系PbTe和CsPbBr中研究了反键价带（ABVBs）与低晶格热导率之间的关系。然后，我们在材料项目数据库中进行了高通量搜索，识别出600多种在价带中具有反键特性的实验稳定二元半导体。从我们的候选列表中，我们对XS族（其中X = K、Rb和Cs为碱金属）的化学键和热输运进行了全面分析。尽管这些材料结构简单，但在室温下它们都表现出小于1 W/(m·K)的超低热导率。我们将超低热导率归因于由于其ABVBs导致的键弱化和声子非谐性增加。我们的结果为理解晶体中的晶格动力学提供了化学直觉，并为寻找具有固有低晶格热导率的材料开辟了一条便捷途径。
