Femtosecond Electron Diffraction Reveals Local Disorder and Local Anharmonicity in Thermoelectric SnSe,Advanced Materials

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Femtosecond Electron Diffraction Reveals Local Disorder and Local Anharmonicity in Thermoelectric SnSe
Advanced Materials ( IF 27.4 ) Pub Date : 2024-03-05 , DOI: 10.1002/adma.202313742
Jingjun Li ₁ , Yingpeng Qi ₁ , Qing Yang ₂ , Luye Yue ₁ , Changyuan Yao ₁ , Zijing Chen _{3,

4} , Sheng Meng _{2,

5,

6} , Dao Xiang _{3,

4,

7,

8} , Jianming Cao _{1,

9}

Affiliation

In addition to long-range periodicity, local disorder, with local structures deviating from the average lattice structure, dominates the physical properties of phonons, electrons, and spin subsystems in crystalline functional materials. Experimentally characterizing the 3D atomic configuration of such a local disorder and correlating it with advanced functions remains challenging. Using a combination of femtosecond electron diffraction, structure factor calculations, and time-dependent density functional theory molecular dynamics simulations, the static local disorder and its local anharmonicity in thermoelectric SnSe are identified exclusively. The ultrafast structural dynamics reveal that the crystalline SnSe is composed of multiple locally correlated configurations dominated by the static off-symmetry displacements of Sn (≈0.4 Å) and such a set of locally correlated structures is termed local disorder. Moreover, the anharmonicity of this local disorder induces an ultrafast atomic displacement within 100 fs, indicating the signature of probable THz Einstein oscillators. The identified local disorder and local anharmonicity suggest a glass-like thermal transport channel, which updates the fundamental insight into the long-debated ultralow thermal conductivity of SnSe. The method of revealing the 3D local disorder and the locally correlated interactions by ultrafast structural dynamics will inspire broad interest in the construction of structure–property relationships in material science.

中文翻译：

飞秒电子衍射揭示热电 SnSe 中的局域无序和局域非谐性

除了长程周期性之外，局部无序（局部结构偏离平均晶格结构）主导着晶体功能材料中声子、电子和自旋子系统的物理性质。通过实验表征这种局部无序的 3D 原子构型并将其与高级功能关联起来仍然具有挑战性。结合飞秒电子衍射、结构因子计算和时间相关密度泛函理论分子动力学模拟，独家识别了热电 SnSe 中的静态局部无序及其局部非谐性。超快结构动力学揭示了晶体 SnSe 由多个局部相关构型组成，这些构型由 Sn 的静态非对称位移 (≈0.4 Å) 主导，这样一组局部相关结构被称为局部无序。此外，这种局部无序的非和谐性会引起 100 fs 内的超快原子位移，这表明可能存在太赫兹爱因斯坦振荡器的特征。所发现的局部无序性和局部不和谐性表明存在类似玻璃的热传输通道，这更新了对长期争论的 SnSe 超低导热系数的基本认识。通过超快结构动力学揭示 3D 局部无序和局部相关相互作用的方法将激发人们对材料科学中结构-性能关系构建的广泛兴趣。

更新日期：2024-03-05

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