化学键“抓紧”：半赫斯勒热电材料延展

半赫斯勒材料同时具有优异的热电性能和力学性能，是一种良好的能源转化材料，有潜力开发先进的热电器件，目前制约其发展的主要阻碍是其固有的脆性以及有限的延展性。

而在面心立方结构中存在的剪切诱导“抓紧键”现象，能够使材料表现出良好的延展性，而半赫斯勒材料的晶体结构是三层嵌套的面心立方结构，其晶体结构中可能同样存在剪切诱导“抓紧键”现象，使其具有潜在优异的延展性。

Fig. 2 | The atomic configurations and dynamic chemical bonds length of TaFeSb before first stress releasing process during the (111)/<–1-12> shear.

来自武汉理工大学理学院的李国栋教授团队，使用第一性原理方法研究了TaFeSb半赫斯勒热电材料的剪切响应，发现了剪切诱导“抓紧键”现象，该“抓紧键”现象被认为是不全位错导致的连续滑移，使材料具有良好的延展性。

该团队除研究了TaFeSb的剪切响应外，还在具有相同结构特征的NbFeSb中同样发现了剪切诱导“抓紧键”现象，而在SnNiY (Y = Ti, Zr, Hf)的剪切响应中，晶体结构逐渐软化来释放应力，两者的差异来源于是否发生晶面解离。

Fig. 4 | The generalized stacking fault energy calculations model and generalized stacking fault energy results of TaFeSb.

最终，剪切诱导“抓紧键”现象被认为是晶体结构沿特定滑移面发生化学键断裂后出现的连续滑移。作者的此项工作揭示了半赫斯勒热电材料潜在的延展性及其本质。相关论文近期发表于npj Computational Materials 10: 61 (2024)。

Fig. 5 | The atomic configurations and dynamic chemical bonds length of SnNiTi before first stress releasing process during the (111)/<–1-12> shear.

Editorial Summary

Half-Heusler materials, with excellent thermoelectric and mechanical properties, are one kinds of excellent energy conversion materials, which is potential on developing advanced thermoelectric devices. At present, the main obstacle to their development is their inherent brittleness and limited ductility. Shear induced “catching bonds” phenomenon has been discovered in face-centered cubic structure, resulting in the excellent ductility. Half-Heusler materials with face-centered cubic sub-lattices may possess shear induced “catching bonds” phenomenon, resulting in the potential excellent ductility.

Fig. 6 | Shear strain dependent relative systematic energy of XFeSb (X = Nb, Ta) and SnNiY (Y = Ti, Zr, Hf) during the (111)/<–1-12> shear.

A research group led by Professor Guodong Li, from the School of Science at Wuhan University of Technology, used the first-principles calculations investigating the shear response of TaFeSb half-Heusler thermoelectric materials and found the shear induced “catching bonds” phenomenon during the shear process, resulting in the excellent ductility. Such shear induced “catching bonds” phenomenon can be considered as the continuous slips caused by partial dislocations. In addition to the investigations on the shear response of TaFeSb, shear-induced “catching bonds” phenomenon have also been found in NbFeSb with the same structural characteristics, while in the shear response of SnNiY (Y = Ti, Zr, Hf), the crystal structures gradually soften to release the stress, whose difference comes from whether the crystal plane cleavage occurs. Finally, the shear-induced “catching bonds” phenomenon can be considered as the continuous slips that occur after the chemical bond breakage along the specific crystal plane.

The research group revealed the potential ductility of the halfi-Heusler thermoelectric material combined with its essence and origin . The relevant work was recently published in npj Computational Materials 10: 61 (2024).

原文Abstract及其翻译

Haoqin Ma, Xiege Huang, Zhongtao Lu, Xiaobin Feng, Bo Duan, Wenjuan Li, Yinhan Liu, Pengcheng Zhai, Guodong Li, Qingjie Zhang

Abstract Half Heusler materials exhibit excellent thermoelectric and mechanical properties, rendering them potential candidates for advanced thermoelectric devices. Currently, the developments on interrelated devices are impeded by their inherent brittleness and limited ductility. Nevertheless, it exists the potential ductility on half Heusler materials with face-centered cubic sub-lattices through the expectation on the occurrence of shear induced ‘catching bonds’ which can result in excellent ductility on other face centered cubic materials. In this work, focus on half Heusler thermoelectric materials XFeSb (X = Nb, Ta) and SnNiY (Y = Ti, Zr, Hf), the shear deformation failure processes are deeply investigated through the first principle calculations. Shear induced ‘catching bonds’ are found on XFeSb (X = Nb, Ta) along the (111)/<-1-12> slip system, which releasing the internal stress and exactly resulting in the potential ductility. According to the thermodynamic criterion based on generalized stacking fault energy, the essence of shear induced ‘catching bonds’ are interpreted as the (111)/<-110> slips formed by several 1/3(111)/<-1-12> partial dislocations motions. During the (111)/<-1-12> shear on SnNiY (Y = Ti, Zr, Hf), the structural integrity is maintained without inducing ‘catching bonds’. Different deformation processes occurred in the identical crystal structure are elucidated through the energy explanation, revealing that shear induced ‘catching bonds’ originate from the crystal plane cleavage on the (111) plane. The present works offer significant advantageous for the assessment and comprehension of shear induced ‘catching bonds’ in other materials, and facilitate the developments of XFeSb (X = Nb, Ta)-based thermoelectric devices with excellent ductility.

摘要半赫斯勒材料具有优异的热电性能和力学性能，有潜力开发先进的热电器件，目前制约其器件发展的主要阻碍是其固有的脆性以及有限的延展性。在面心立方结构中存在的剪切诱导“抓紧键”现象，能够使材料表现出良好的延展性，而半赫斯勒材料的晶体结构是三层嵌套的面心立方结构，其晶体结构中可能也同样存在剪切诱导“抓紧键”现象，使其具有潜在优异的延展性。本文以半赫斯勒热电材料XFeSb (X = Nb, Ta)和SnNiY (Y = Ti, Zr, Hf)作为研究对象，通过第一性原理方法研究了其剪切变形失效过程。XFeSb (X = Nb, Ta)沿(111)/<-1-12>滑移系剪切时出现了剪切诱导“捕获键”现象，释放了内应力，从而使材料具有潜在的延展性。基于广义堆垛层错能的热动力学准则，该剪切诱导“抓紧键”现象被认为是1/3(111)/<-1-12>不全位错运动形成的(111)/<-110>滑移。在SnNiY (Y = Ti, Zr, Hf)沿(111)/<-1-12>滑移系剪切的过程中，结构始终保持完整性，不会产生剪切诱导“抓紧键”现象。通过能量解释，揭示了剪切诱导“抓紧键”现象源于(111)平面上的晶面解理。本研究为评估和理解其他材料中的剪切诱导“抓紧键”现象提供了理论基础，并促进了具有优异延展性的XFeSb (X = Nb, Ta)基热电器件的开发。