热导率是材料最基本的物理性能之一，更是热电能量转换等材料的核心参数，因此快速判断和预测材料的热导率具有重要的科学意义和应用价值。在半导体材料中，晶格热导率（L）通常占主导，其数值大小取决于从原子/晶格到晶粒等几乎全尺度的结构特征和多种物理作用过程。材料基因工程基于性能判据和高通量计算，为特定性能材料的筛选提供了新的理念和方法。然而，晶格热导率涉及多种物理机制和过程，难以提出一种兼顾效率（简洁直观）与准确性（丰富内涵）的筛选判据，尤其是对结构复杂、种类繁多的新型化合物。
日前，中国科学院上海硅酸研究所史迅、陈立东研究员联合上海大学杨炯教授、上海交通大学魏天然助理教授等，以近年来热电、光电等领域备受关注的铜/银基三元硫属化合物为示范，基于73种材料的晶格热导率数据和晶体学信息，提出了快速预测材料晶格热导率的直观判据——阴阳离子数失配度δ = (Ncation-Nanion)/Nanion）。作者以具有较大离子数失配的Cu4Sn7S16（d = -0.3125）复杂结构化合物为例，精细解析了材料的晶体结构和晶格振动模式，分析了低温热输运性质，建立了表观阴阳离子数失配与微观结构畸变、晶胞复杂化以及热导率的关联，系统阐释了该判据的科学内涵。接下来，作者基于此判据预测了一种结构未知的低热导新材料Cu2Sn4S9（d = -0.33），并通过实验进行了验证。这一简洁直观的离子数失配判据很好地解释了实验现象，筛选出了新的低晶格热导化合物，有望进一步推广到其他复杂化合物体系，为低热导化合物的快速筛选提供指导。
该文近期发表于npj Computational Materials 6: 81 (2020)，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。
图2阴阳离子数失配对热输运的影响示意图
Figure 2. Effects of δ on thermal transport.
Number mismatch between cations and anions as an indicator for low lattice thermal conductivity in chalcogenides
Tingting Deng,|| Tian-Ran Wei,|| Hui Huang, Qingfeng Song, Kunpeng Zhao, Pengfei Qiu, Jiong Yang,* Lidong Chen, Xun Shi*
Thermal conductivity is one of the most fundamental properties of materials with the value being determined by nearly all-scale structural features and multiple physical processes. Rapidly judging material’s thermal conductivity is extremely important but challenging for the applications. The material genome paradigm offers a revolutionary way to efficiently screen and discover materials with designed properties by using accessible indicators. But such a performance indicator for thermal conductivity is quite difficult to propose due to the existence of multiple mechanisms and processes, especially for the materials with complex structures such as chalcogenides. In this study, the number mismatch between cations and anions is proposed as a practical performance indicator for lattice thermal conductivity in complex copper and silver chalcogenides, which can be used to explain the observed experimental data and find new low thermal conductivity materials. Such a number mismatch brings about rich phenomena to affect thermal conductivity including the complication of the unit cell and the creation of chemical hierarchy, point defects, rattling modes and lone pair electrons. It is expected that this rich-connotation performance indicator can be also extended to other complex materials to discover designed thermal conductivities.