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arXiv 1209.3485cond-mat.mes-hallcond-mat.stat-mech
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用平衡和非平衡分子动力学计算晶体界面的热导

Thermal conductance at the interface between crystals using equilibrium and non-equilibrium molecular dynamics

Samy Merabia, Konstantinos Termentzidis

摘要:

在本文中,我们比较了非平衡态(NEMD)和平衡态(EMD)分子动力学方法计算固体界面热导的结果。我们建议使用平衡模拟测量每个固体的热致能量波动的衰减来探测热导。我们还表明,NEMD和EMD给一般来说不一致的结果的热导:绿色久保模拟探测两个固体之间的Landauer电导假设声子的界面两侧处于平衡状态。另一方面,我们表明,NEMD给访问的平衡界面电导一致的界面通量描述在每个固体中的声子输运。差异可能很大,并且对于通常的半导体之间的界面通常达到因子5。我们分析了有限尺寸效应的两个确定的界面热导,并表明,平衡模拟遭受严重的尺寸效应相比,NEMD。我们还比较了上述两种方法(EMD和NEMD)关于一系列质量不匹配的Lennard-Jones固体的界面电导的预测。我们发现,用EMD得到的Kapitza电导可以很好地描述使用经典的扩散失配模型(DMM)。另一方面,NEMD模拟结果与声失配模型(AMM)的平衡概括是一致的。这些考虑是很重要的,在合理化以前的结果,使用分子动力学,并有助于查明物理散射机制发生在原子之间的固体,这是一个先决条件,以了解真实界面的界面传热。

英文摘要:

In this article, we compare the results of non-equilibrium (NEMD) and equilibrium (EMD) molecular dynamics methods to compute the thermal conductance at the interface between solids. We propose to probe the thermal conductance using equilibrium simulations measuring the decay of the thermally induced energy fluctuations of each solid. We also show that NEMD and EMD give generally speaking inconsistent results for the thermal conductance: Green Kubo simulations probe the Landauer conductance between two solids which assumes phonons on both sides of the interface to be at equilibrium. On the other hand, we show that NEMD give access to the out-of-equilibrium interfacial conductance consistent with the interfacial flux describing phonon transport in each solid. The difference may be large and reaches typically a factor 5 for interfaces between usual semi-conductors. We analyze finite size effects for the two determinations of the interfacial thermal conductance, and show that the equilibrium simulations suffer from severe size effects as compared to NEMD. We also compare the predictions of the two above mentioned methods -EMD and NEMD- regarding the interfacial conductance of a series of mass mismatched Lennard-Jones solids. We show that the Kapitza conductance obtained with EMD can be well described using the classical diffuse mismatch model (DMM). On the other hand, NEMD simulations results are consistent with a out-of-equilibrium generalisation of the acoustic mismatch model (AMM). These considerations are important in rationalizing previous results obtained using molecular dynamics, and help in pinpointing the physical scattering mechanisms taking place at atomically perfect interfaces between solids, which is a prerequesite to understand interfacial heat transfer across real interfaces.

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