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Phonon transport properties of two-dimensional electride Ca_2N-A first-principles study

机译:二维电子Ca_2N-A第一性原理的声子输运性质

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摘要

We investigate phonon transport in dicalcium nitride (Ca2N), an electride with two-dimensional confined electron layers, using first-principles density functional theory and the phonon Boltzmann transport equation. The in-plane (kappa([100])) and out-of-plane (kappa([001])) lattice thermal conductivities at 300 K are found to be 11.72 W m(-1) K-1 and 2.50 W m(-1) K-1 , respectively. Spectral analysis of lattice thermal conductivity shows that similar to 85% of kappa([100] )and kappa([001]) is accumulated by phonons with frequencies less than 5.5 THz and 2.5 THz, respectively. Modal decomposition of lattice thermal conductivity further reveals that the optical phonons contribute to similar to 68% and similar to 55% of overall kappa([100]) and kappa([001]), respectively. Phonon dispersion suggests that the large optical phonon contribution is a result of low frequency optical phonons with high group velocities and the lack of phonon bandgap between the acoustic and optical phonon branches. We find that the optical phonons with frequencies below similar to 5.5 THz have similar three-phonon phase space and scattering rates as acoustic phonons. Comparison of the contributions from emission and absorption processes reveals that the three-phonon phase space and scattering rates of phonons-optical or acoustic-with frequencies below 5.5 THz are largely dominated by absorption processes. We conclude that the large contribution to lattice thermal conductivity by optical phonons is due to the presence of multiple low frequency optical phonon modes with high group velocities and similar phase space and scattering rates as the acoustic phonons. This study provides the frequency and temperature dependent lattice thermal conductivity and insights into phonon transport in Ca2N, both of which have important implications for the development of Ca2N based devices. Published by AIP Publishing.
机译:我们使用第一原理密度泛函理论和声子玻尔兹曼输运方程研究了氮化钙(Ca2N)中的声子输运,该氮化物具有二维约束电子层。发现300 K时的面内(kappa([100]))和面外(kappa([001]))的晶格热导率分别为11.72 W m(-1)K-1和2.50 W m (-1)K-1。晶格热导率的光谱分析表明,频率低于5.5 THz和2.5 THz的声子累积了大约85%的kappa([100])和kappa([001])。晶格热导率的模态分解进一步表明,光子分别占总κ([100])和κ([001])的68%和55%。声子色散表明,较大的光子声子贡献是由于具有高群速度的低频光子和声子和光子声子分支之间缺乏声子带隙所致。我们发现,频率低于5.5 THz的光子与声子具有相似的三声子相空间和散射率。通过比较发射和吸收过程的贡献,发现在低于5.5 THz的频率下,声子的光子或声子的三声子相空间和散射率主要受吸收过程支配。我们得出的结论是,声子对晶格热导率的巨大贡献是由于存在多个低频声子模式,这些声子模式具有高的声速,并且相空间和散射率与声子类似。这项研究提供了频率和温度相关的晶格热导率,并深入了解了Ca2N中的声子传输,这两者对于基于Ca2N的器件的开发都具有重要意义。由AIP Publishing发布。

著录项

  • 来源
    《Applied Physics Letters》 |2018年第13期|131902.1-131902.5|共5页
  • 作者单位

    Georgia Inst Technol, GW Woodruff Sch Mech Engn, Atlanta, GA 30332 USA;

    Georgia Inst Technol, GW Woodruff Sch Mech Engn, Atlanta, GA 30332 USA;

    Oak Ridge Natl Lab, Ctr Nanophase Mat Sci, POB 2009, Oak Ridge, TN 37831 USA;

    Georgia Inst Technol, GW Woodruff Sch Mech Engn, Atlanta, GA 30332 USA;

    Georgia Inst Technol, GW Woodruff Sch Mech Engn, Atlanta, GA 30332 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
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  • 入库时间 2022-08-18 03:13:56

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