单层石墨烯热膨胀系数的分子动力学研究

发布时间：2018-04-29 11:33

本文选题：石墨烯 + 面热膨胀系数　；参考：《西南科技大学》2017年硕士论文

【摘要】：本文采用分子动力学模拟的方法,对无缺陷和带空位缺陷单层石墨烯的面热膨胀系数进行了研究。重点讨论了温度、模型尺寸及采样区域面积等对单层石墨烯的面热膨胀系数的影响。研究结果表明,无缺陷和带空位缺陷单层石墨烯的面热膨胀系数随温度的变化均呈非线性变化,并且在很大温度范围内均为负值(热收缩),当温度高于600 K 时,面热膨胀系数随温度的变化很小,几乎处于无热膨胀状态。在无缺陷单层石墨烯的面热膨胀系数的研究中,还发现石墨烯的模型尺寸和采样区域面积对面热膨胀系数的变化有着较大的影响。当石墨烯的模型尺寸小于一定尺寸时(此尺寸称为临界值),具有尺寸效应,随着模型尺寸的增大石墨烯的面热膨胀系数绝对值变小,且此时,采样区域面积大于模型尺寸的一定比例时,才可得较稳定的数据或易于收敛。当石墨烯的模型尺寸大于临界值时,无尺寸效应,随着模型尺寸的增大石墨烯的面热膨胀系数无明显变化,此时,采样区域面积大于一定尺寸即可得到较稳定的数据或易于收敛,与模型尺寸无关。在本研究中根据实验数据,提出了一个经验公式,在指定温度范围内可计算出无缺陷单层石墨烯的面热膨胀系数。此外,本文对于带有空位缺陷的单层石墨烯的面热膨胀系数也进行了研究。研究结果发现,在较大的温度范围随着缺陷比例的增加面热膨胀系数的绝对值减小;带集中空位缺陷的单层石墨烯,其面热膨胀系数的绝对值相对小于带分散空位缺陷的单层石墨烯的面热膨胀系数的绝对值,特别是在缺陷比例较大时更为明显。
[Abstract]:In this paper, the surface thermal expansion coefficients of graphene monolayers with and without defects were studied by molecular dynamics simulation. The effects of temperature, model size and sampling area on the surface thermal expansion coefficient of graphene monolayer were discussed. The results show that the surface thermal expansion coefficient of graphene monolayer without defects and with vacancy defects shows nonlinear variation with temperature, and is negative in a wide range of temperatures (thermal shrinkage, when the temperature is higher than 600K), The coefficient of surface thermal expansion varies little with temperature and is almost in the state of no thermal expansion. In the study of the surface thermal expansion coefficient of graphene monolayer without defects, it is also found that the model size of graphene and the change of the coefficient of thermal expansion across the sample area have a great influence on the surface thermal expansion coefficient of graphene monolayer. When the model size of graphene is less than a certain size (this size is called critical value, it has size effect, the surface thermal expansion coefficient of graphene becomes smaller with the increase of model size, and at this time, Only when the sampling area is larger than a certain proportion of the model size, can stable data be obtained or converged easily. When the model size of graphene is larger than the critical value, there is no size effect, and the surface thermal expansion coefficient of graphene does not change obviously with the increase of the model size. The sample area is larger than a certain size, and the data can be stable or convergent, independent of the model size. Based on the experimental data, an empirical formula is proposed to calculate the surface thermal expansion coefficient of graphene monolayer without defects within a specified temperature range. In addition, the surface thermal expansion coefficient of graphene monolayer with vacancy defects is also studied. The results show that the absolute value of thermal expansion coefficient decreases with the increase of defect ratio in a large temperature range. The absolute value of the surface thermal expansion coefficient is relatively smaller than that of the monolayer graphene with dispersed vacancy defects, especially when the defect ratio is large.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1

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