Wang Xinyu, Wang Man, Hong Yang, Wang Zongrong, Zhang Jingchao
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
Phys Chem Chem Phys. 2017 Sep 13;19(35):24240-24248. doi: 10.1039/c7cp04219a.
The transition between coherent and incoherent phonon transport in a graphene (GRA) and nitrogenated holey graphene (CN) superlattice is investigated by non-equilibrium molecular dynamics (NEMD) simulation. We find that the thermal conductivity of the GRA-CN superlattice is much lower than those of graphene and CN, and exhibits a positive correlation with the system length. Owing to three mechanisms, i.e., phonon wave interference, phonon confinement and phonon interface scattering, the calculated thermal conductivity shows a decreasing trend at small period length scales and gradually increases at large period length scales. The coherence length of the superlattice at 300 K is 4.43 nm, which is independent of the total length. In addition, the effects of temperature and uniaxial tensile strain on phonon transport are investigated. At 100 K, the coherent phonons play a more dominating role in the superlattice and the responding coherence length is enlarged to 7.38 nm. On the other hand, tensile strain can effectively reduce the thermal conductivity, which results from the phonon softening.
通过非平衡分子动力学（NEMD）模拟研究了石墨烯（GRA）和氮化多孔石墨烯（CN）超晶格中相干声子输运与非相干声子输运之间的转变。我们发现，GRA-CN超晶格的热导率远低于石墨烯和CN的热导率，并且与系统长度呈正相关。由于声子波干涉、声子限制和声子界面散射这三种机制，计算得到的热导率在小周期长度尺度上呈下降趋势，而在大周期长度尺度上逐渐增加。超晶格在300 K时的相干长度为4.43 nm，与总长度无关。此外，还研究了温度和单轴拉伸应变对声子输运的影响。在100 K时，相干声子在超晶格中起更主导的作用，相应的相干长度增大到7.38 nm。另一方面，拉伸应变可有效降低热导率，这是由声子软化导致的。
