Grain boundaries in graphene are inherent in wafer-scale samples prepared by chemical vapor deposition. They can strongly influence the mechanical properties and electronic and heat transport in graphene. In this work, we employ extensive molecular dynamics simulations to study thermal transport in large suspended polycrystalline graphene samples. Samples of different controlled grain sizes are prepared by a recently developed efficient multiscale approach based on the phase field crystal model. In contrast to previous works, our results show that the scaling of the thermal conductivity with the grain size implies bimodal behavior with two effective Kapitza lengths. The scaling is dominated by the out-of-plane (flexural) phonons with a Kapitza length that is an order of magnitude larger than that of the in-plane phonons. We also show that, to get quantitative agreement with the most recent experiments, quantum corrections need to be applied to both the Kapitza conductance of grain boundaries and the thermal conductivity of pristine graphene, and the corresponding Kapitza lengths must be renormalized accordingly.

中文翻译：

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大规模分子动力学模拟的多峰石墨烯中热输运的双峰粒度定标

石墨烯中的晶界是通过化学气相沉积制备的晶圆级样品所固有的。它们会极大地影响石墨烯的机械性能以及电子和热传递。在这项工作中，我们采用了广泛的分子动力学模拟来研究大型悬浮多晶石墨烯样品中的热传递。通过最近开发的基于相场晶体模型的高效多尺度方法，可以制备出具有不同受控晶粒度的样品。与以前的工作相反，我们的结果表明，热导率随晶粒尺寸的缩放暗示了具有两个有效Kapitza长度的双峰行为。比例缩放由Kapitza长度比平面内声子大一个数量级的平面外（弯曲）声子控制。我们还表明，