Xu Zhiyuan, Xia Qiong, Gao Guoying
School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China.
Phys Chem Chem Phys. 2022 Oct 19;24(40):24917-24923. doi: 10.1039/d2cp01395a.
Based on first-principles calculations in combination with the Boltzmann transport theory, we investigate the effects of onsite Coulomb interaction and strain on the lattice thermal conductivity of the KAgSe monolayer, a recently discovered 2D thermoelectric system with a low lattice thermal conductivity when the onsite Coulomb interaction was not considered (X. Zhang, C. Liu, Y. Tao, Y. Li, Y. Guo, Y. Chen, X. C. Zeng and J. Wang, , 2020, , 2001200). Our calculations reveal that the onsite Coulomb interaction leads to an increase in the lattice thermal conductivity from 1.22 to 1.82 W m K at room temperature due to the increased phonon group velocity and relaxation time. However, with onsite Coulomb interaction, small 3% biaxial tensile strain can give rise to a 75% considerable decrease in the lattice thermal conductivity at room temperature, from 1.82 to 0.45 W m K, which is also much lower than the lattice thermal conductivity of 1.22 W m K without onsite Coulomb interaction and strain. The strain induced decrease of phonon group velocity and enhancement of lattice anharmonicity (large Grüneisen parameter and phase space volume) are responsible for the reduced lattice thermal conductivity. The present work highlights that the onsite Coulomb interaction is indispensable when determining the lattice thermal conductivity of 2D KAgSe, and small tensile strain can greatly decrease the lattice thermal conductivity.
基于第一性原理计算并结合玻尔兹曼输运理论，我们研究了在位库仑相互作用和应变对KAgSe单层晶格热导率的影响。KAgSe单层是一种最近发现的二维热电系统，在不考虑在位库仑相互作用时具有较低的晶格热导率（X. Zhang, C. Liu, Y. Tao, Y. Li, Y. Guo, Y. Chen, X. C. Zeng和J. Wang, 2020, 2001200）。我们的计算表明，由于声子群速度和弛豫时间的增加，在位库仑相互作用导致室温下晶格热导率从1.22 W m⁻¹ K⁻¹增加到1.82 W m⁻¹ K⁻¹。然而，在存在在位库仑相互作用的情况下，3%的小双轴拉伸应变会导致室温下晶格热导率大幅下降75%，从1.82 W m⁻¹ K⁻¹降至0.45 W m⁻¹ K⁻¹，这也远低于不存在在位库仑相互作用和应变时的晶格热导率1.22 W m⁻¹ K⁻¹。应变引起的声子群速度降低和晶格非谐性增强（大的格林艾森参数和相空间体积）是晶格热导率降低的原因。本工作强调，在确定二维KAgSe的晶格热导率时，在位库仑相互作用是不可或缺的，并且小的拉伸应变会大大降低晶格热导率。
