Lattice thermal transport in superhard hexagonal diamond and wurtzite boron nitride: A comparative study with cubic diamond and cubic boron nitride
Lattice thermal transport in superhard hexagonal diamond and wurtzite boron nitride: A comparative study with cubic diamond and cubic boron nitride
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DOI：
10.1016/j.carbon.2018.06.025
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发表时间：
2018-11-01
期刊：
影响因子：
10.9
通讯作者：
Wang, Yan
中科院分区：
文献类型：
--
作者：
Chakraborty, Pranay;Xiong, Guoping;Wang, Yan
六方金刚石（h-C）和纤锌矿氮化硼（w-BN）是最近发现的两种超硬材料，其硬度相当于甚至比立方金刚石（c-C）和立方氮化硼（c-BN）更硬。为了了解晶格结构对这些材料热传输的影响，我们进行第一性原理计算来研究它们的谐波和非谐波晶格特性。由于强 C-C 或 B-N 键，h-C 和 w-BN 具有超过金属整体热导率的高晶格热导率 (k(L))，尽管低于其立方体对应物。通过分析声子能带结构和3-声子散射相空间的体积，我们将六方相较低的k(L)归因于其3-声子散射相空间的体积比立方相更大。此外，我们发现 125 GPa 的高压会导致这些材料的 k(L) 增加两到三倍，因为压力扩大了光声声子带隙，从而减少了 3 声子散射相空间的体积。这项工作揭示了晶格结构和压力对声子散射和传输的显着影响，这对于超硬材料的应用至关重要。 (C) 2018 Elsevier Ltd. 保留所有权利。
Hexagonal diamond (h-C) and wurtzite boron nitride (w-BN) are two superhard materials recently identified to be comparable to or even harder than their cubic counterparts, cubic diamond (c-C) and cubic boron nitride (c-BN). To understand the effect of lattice structure on thermal transport in these materials, we conduct first-principles calculations to investigate their harmonic and anharmonic lattice properties. Owing to the strong C-C or B-N bonds, h-C and w-BN are found to have a high lattice thermal conductivity (k(L)) exceeding the overall thermal conductivity of metals, albeit lower than that of their cubic counterparts. By analyzing the phonon band structure and volume of the 3-phonon scattering phase space, we attribute the lower k(L) of the hexagonal phases to their larger volume of 3-phonon scattering phase space than the cubic ones. Moreover, we reveal that a high pressure of 125 GPa leads to a two-to three-fold increase in the k(L) of these materials, because the pressure enlarges the optical-acoustic phonon bandgap and thus reduces the volume of the 3-phonon scattering phase space. This work uncovers the significant effect of lattice structure and pressure on phonon scattering and transport, which is crucial for the application of superhard materials. (C) 2018 Elsevier Ltd. All rights reserved.