基于分子动力学的石墨炔纳米带空位缺陷的导热特性

空位缺陷石墨炔比完整石墨炔更贴近实际材料,而空位缺陷的多样性可导致更丰富的导热特性,因此模拟各种空位缺陷对热导率的影响显得尤为重要.采用非平衡分子动力学方法,通过在纳米带长度方向上施加周期性边界条件,基于AIREBO(adaptive intermolecular reactive empirical bond order)势函数描述碳-碳原子间的相互作用,模拟了300 K时单层石墨炔纳米带乙炔链上单空位缺陷和双空位缺陷以及苯环上单空位缺陷对其热导率的影响,利用Fourier定律计算热导率.模拟结果表明,对于几十纳米尺度范围内的石墨炔纳米带热导率,1)由于声子的散射集中和声子倒逆过程增强,与完美无缺陷的石墨炔纳米带相比,空位缺陷会导致石墨炔纳米带热导率的下降;2)由于声子态密度匹配程度高低的不同,相比于乙炔链上的空位缺陷,苯环的空位缺陷对石墨炔纳米带热导率影响更大,乙炔链上空位缺陷数量对石墨炔纳米带热导率的影响明显;3)由于尺寸效应问题,随着长度增加,石墨炔纳米带热导率会相应增大.本文的研究可为在一定尺度下进行石墨炔纳米带热导率的调控问题提供参考.

Based on the molecular dynamics characteristic research of heat conduction of graphyne nanoribbons with vacancy defects

As a kind of nano-material, graphyne nanoribbon has some physical properties and its properties should be studied for its better usage. In the process of preparing graphyne nanoribbons, it is possible that vacancy defects exist in the lattice structure, which will affect the physical properties of the graphyne nanoribbons. The flotation of graphyne is closer to the actual situation in engineering than the complete graphyne nanoribbons, and the diversity of vacancy defects can lead to various thermal conductivities, so it is very important to simulate the effects of various vacancy defects on thermal conductivity. In order to better predicte and control heat transfer characteristics of graphyne nanoribbons, this paper focuses on the effects of vacancy defects on the heat transfer characteristics of graphyne nanoribbons. According to the different cutting directions of graphyne nanoribbons, two different types of graphyne nanoribbons are obtained, i.e., armchair type and zigzag type. We compare the effects of vacancy defects on the thermal conductivity of two different chiral graphynes nanoribbons to improve the persuasiveness of the conclusion. In this paper, non-equilibrium molecular dynamics method is adopted, by applying periodic boundary conditions in the length direction of the nanoribbons, the interaction between the carbon-carbon atoms is described based on a potential function of adaptive intermolecular reactive empirical bond order (AIREBO). At 300 K, the effects of single vacancy defect in the acetylene chain, single vacancy defect in the benzene ring or double vacancy defects in the acetylene chain on the thermal conductivities of single-layer graphyne nanoribbons are simulated. Fourier's law is used to calculate the thermal conductivities of graphyne nanoribbons. The simulation results show that for the thermal conductivity of graphyne nanoribbons in a-few-dozen nanometer range:1) as a result of the phonon scattering and enhanced phonon Umklapp process, the graphyne nanoribbons with vacancy defects will cause the thermal conductivity to decrease and becomes lower than that of the complete graphyne nanoribbons; 2) due to the difference in phonon density-of-states matching degree, the vacancy defect in the benzene ring of graphyne nanoribbons has a greater effect on the thermal conductivity than that of vacancy defect in the acetylene chain of graphyne nanoribbons, the vacancy defects have a strong influence on the thermal conductivity of in the acetylene chain of graphyne nanoribbons; 3) because of the influence of size effect, the thermal conductivity of graphyne nanoribbon increases with length increasing. In this paper, the research of the thermal conductivity of graphyne nanoribbon provides the reference for controlling their thermal conductivity on a certain scale.