Abstract The cage structure and low lattice thermal conductivity κ L make the schwarzites a suitable candidate for building the host-guest system favorable for thermoelectric applications. In host-guest system, the guest atoms in cages play a crucial role for reducing κ L . However, the underlying mechanism on the thermal conductivity reduction remains unclear. In this work, the authors unveil, through atomic simulations, the working principles of guest atoms in schwarzites by highlighting the relationship between thermal transport properties and rattling motions of guest atoms. It has been found that local vibration of the “on-center” guest atoms at low temperatures gives rise to a single hybridized mode, while the positions of guest atoms at high temperatures deviate severely from the center of cages yielding blue-shifted hybridized modes. These blue-shifted hybridized modes are responsible for the reduction of the phonon relaxation time in a wide range of frequencies. Based on these findings, the authors propose guidelines for reducing κ L in schwarzites by properly tuning the frequency of one hybridized mode. Further reduction of κ L can be achieved by simultaneously introducing multiple hybridized modes with different characteristic frequencies. This study provides insights to the controllable thermal transport properties in schwarzites by engineering the hybridized phonon modes.

中文翻译：

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通过设计杂化声子模式降低 Schwarzites 的晶格热导率

摘要 笼状结构和低晶格热导率 κ L 使施瓦茨石成为构建有利于热电应用的主客体系统的合适候选者。在主客体系统中，笼中的客体原子对降低 κ L 起着至关重要的作用。然而，热导率降低的潜在机制仍不清楚。在这项工作中，作者通过原子模拟揭示了施瓦茨石中客体原子的工作原理，强调了热传输特性与客体原子的嘎嘎作响运动之间的关系。已经发现，低温下“中心”客体原子的局部振动会产生单一的杂化模式，而高温下客体原子的位置严重偏离笼子的中心，产生蓝移杂化模式。这些蓝移杂化模式负责在很宽的频率范围内减少声子弛豫时间。基于这些发现，作者提出了通过适当调整一种杂交模式的频率来减少 schwarzites κ L 的指导方针。通过同时引入具有不同特征频率的多种混合模式，可以进一步降低 κ L 。这项研究通过设计杂化声子模式，为了解 schwarzites 中的可控热传输特性提供了见解。通过同时引入具有不同特征频率的多种混合模式，可以进一步降低 κ L 。这项研究通过设计杂化声子模式，为了解 schwarzites 中的可控热传输特性提供了见解。通过同时引入具有不同特征频率的多种混合模式，可以进一步降低 κ L 。这项研究通过设计杂化声子模式，为了解 schwarzites 中的可控热传输特性提供了见解。