Jin Miaomiao, Khafizov Marat, Jiang Chao, Zhou Shuxiang, Marianetti Chris A, Bryan Matthew S, Manley Michael E, Hurley David H
Department of Nuclear Engineering, The Pennsylvania State University, 205 Hallowell Bldg, University Park, PA 16802, United States of America.
Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W 19th Ave, Columbus, OH 43210, United States of America.
J Phys Condens Matter. 2021 May 28;33(27). doi: 10.1088/1361-648X/abdc8f.
Computing vibrational properties of crystals in the presence of complex defects often necessitates the use of (semi-)empirical potentials, which are typically not well characterized for perfect crystals. Here we explore the efficacy of a commonly used embedded-atomempirical interatomic potential for the UThOsystem, to compute phonon dispersion, lifetime, and branch specific thermal conductivity. Our approach for ThOinvolves using lattice dynamics and the linearized Boltzmann transport equation to calculate phonon transport properties based on second and third order force constants derived from the empirical potential and from first-principles calculations. For UO, to circumvent the accuracy issues associated with first-principles treatments of strong electronic correlations, we compare results derived from the empirical interatomic potential to previous experimental results. It is found that the empirical potential can reasonably capture the dispersion of acoustic branches, but exhibits significant discrepancies for the optical branches, leading to overestimation of phonon lifetime and thermal conductivity. The branch specific conductivity also differs significantly with either first-principles based results (ThO) or experimental measurements (UO). These findings suggest that the empirical potential needs to be further optimized for robust prediction of thermal conductivity both in perfect crystals and in the presence of complex defects.
在存在复杂缺陷的情况下计算晶体的振动特性通常需要使用（半）经验势，而这些势对于完美晶体的表征通常并不完善。在此，我们探讨了一种常用于UThO体系的嵌入原子经验原子间势在计算声子色散、寿命和特定分支热导率方面的有效性。我们对ThO的研究方法包括使用晶格动力学和线性化玻尔兹曼输运方程，基于从经验势和第一性原理计算得出的二阶和三阶力常数来计算声子输运性质。对于UO，为了规避与强电子关联的第一性原理处理相关的精度问题，我们将从经验原子间势得出的结果与先前的实验结果进行比较。结果发现，经验势能够合理地捕捉声学支的色散，但对于光学支存在显著差异，导致声子寿命和热导率被高估。特定分支的电导率与基于第一性原理的结果（ThO）或实验测量结果（UO）也有显著差异。这些发现表明，为了在完美晶体以及存在复杂缺陷的情况下可靠地预测热导率，经验势需要进一步优化。
