Liu Gang, Wang Haifeng, Gao Yan, Zhou Jian, Wang Hui
School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023, China.
Department of Physics, College of Science, Shihezi University, Xinjiang 832003, China.
Phys Chem Chem Phys. 2017 Jan 25;19(4):2843-2849. doi: 10.1039/c6cp07367k.
Borophene (boron sheet) as a new type of two-dimensional (2D) material was grown successfully recently. Unfortunately, the structural stability of freestanding borophene is still an open issue. Theoretical research has found that full hydrogenation can remove such instability, and the product is called borophane. In this paper, using first-principles calculations we investigate the lattice dynamics and thermal transport properties of borophane. The intrinsic lattice thermal conductivity and the relaxation time of borophane are investigated by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. We find that the intrinsic lattice thermal conductivity of borophane is anisotropic, as the higher value (along the zigzag direction) is about two times of the lower one (along the armchair direction). The contributions of phonon branches to the lattice thermal conductivities along different directions are evaluated. It is found that both the anisotropy of thermal conductivity and the different phonon branches which dominate the thermal transport along different directions are decided by the group velocity and the relaxation time of phonons with very low frequency. In addition, the size dependence of thermal conductivity is investigated using cumulative thermal conductivity. The underlying physical mechanisms of these unique properties are also discussed in this paper.
硼烯（硼片）作为一种新型二维材料，近期已成功制备出来。遗憾的是，独立硼烯的结构稳定性仍是一个悬而未决的问题。理论研究发现，完全氢化可以消除这种不稳定性，其产物被称为硼烷。本文采用第一性原理计算方法，研究了硼烷的晶格动力学和热输运性质。基于第一性原理计算，通过求解声子玻尔兹曼输运方程（BTE），研究了硼烷的本征晶格热导率和弛豫时间。我们发现硼烷的本征晶格热导率是各向异性的，较高值（沿锯齿方向）约为较低值（沿扶手椅方向）的两倍。评估了声子分支对沿不同方向晶格热导率的贡献。结果表明，热导率的各向异性以及主导不同方向热输运的不同声子分支，均由低频声子的群速度和弛豫时间决定。此外，利用累积热导率研究了热导率的尺寸依赖性。本文还讨论了这些独特性质的潜在物理机制。
