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Size effects in molecular dynamics thermal conductivity predictions

机译：分子动力学热导率预测中的尺寸效应

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摘要

We predict the bulk thermal conductivity of Lennard-Jones argon and Stillinger-Weber silicon using the Green-Kubo (GK) and direct methods in classical molecular dynamics simulations. While system-size-independent thermal conductivities can be obtained with less than 1000 atoms for both materials using the GK method, the linear extrapolation procedure [Schelling et al., Phys. Rev. B 65, 144306 (2002)] must be applied to direct method results for multiple system sizes. We find that applying the linear extrapolation procedure in a manner consistent with previous researchers can lead to an underprediction of the GK thermal conductivity (e.g., by a factor of 2.5 for Stillinger-Weber silicon at a temperature of 500 K). To understand this discrepancy, we perform lattice dynamics calculations to predict phonon properties and from these, length-dependent thermal conductivities. From these results, we find that the linear extrapolation procedure is only accurate when the minimum system size used in the direct method simulations is comparable to the largest mean-free paths of the phonons that dominate the thermal transport. This condition has not typically been satisfied in previous works. To aid in future studies, we present a simple metric for determining if the system sizes used in direct method simulations are sufficiently large so that the linear extrapolation procedure can accurately predict the bulk thermal conductivity.
机译：我们使用Green-Kubo（GK）和经典分子动力学模拟中的直接方法预测Lennard-Jones氩气和Stillinger-Weber硅的体导热系数。尽管使用GK方法在两种材料中都可以获得小于1000个原子的与系统大小无关的热导率，但线性外推程序[Schelling等，Phys。修订版B 65，144306（2002）]必须用于多种系统尺寸的直接方法结果。我们发现，以与以前的研究人员一致的方式应用线性外推程序可能会导致GK热导率的预测不足（例如，在500 K的温度下，Stillinger-Weber硅的系数是2.5）。为了理解这种差异，我们执行晶格动力学计算以预测声子性质，并根据这些与长度相关的热导率进行预测。从这些结果中，我们发现，仅当直接方法仿真中使用的最小系统尺寸与主导热传输的声子的最大无均值路径相当时，线性外推程序才是准确的。在以前的工作中通常不满足此条件。为了帮助将来的研究，我们提出了一种简单的度量标准，用于确定直接方法模拟中使用的系统大小是否足够大，以便线性外推程序可以准确地预测体导热率。

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  • 来源
    《Physical review》 |2010年第21期|P.214305.1-214305.10|共10页
  • 作者

    D. P. Sellan; E. S. Landry; J. E. Turney; A. J. H. McGaughey; C. H. Amon;

  • 作者单位

    Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G8;

    rnDepartment of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA;

    rnDepartment of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA;

    rnDepartment of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA;

    rnDepartment of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G8 Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA;

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  • 正文语种 eng
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  • 关键词

    classical transport;

    机译：古典运输;

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