单层黑磷温度依赖下力学性能的分子动力学模拟研究
发布时间：2019-07-04 17:48
【摘要】：黑磷作为继石墨烯之后又一种新型二维材料,由于其自身非常优异的光学特性与电学特性受到了来自世界各国的科研工作者们的共同关注。黑磷是磷这种元素的同素异形体中最稳定的一种形态,其晶格为多个六圆环相互连接而组成的正交结构。黑磷在前几年刚刚被科学家们发现不久,现如今对于黑磷这种新型二维材料的研究还刚刚起步,相关文献中有关黑磷的电学性能、力学性能特别是不同温度下的力学性能的报道与研究还比较少。本文针对黑磷在研究中存在的亟待解决的问题,采用分子动力学模拟的方法研究单层黑磷在4.2K、100K、200K、300K、400K五种不同梯度温度下单双轴拉伸及纯剪切时的力学性能。此外还模拟研究了单层黑磷的纯弯曲的力学性能,主要研究内容与成果如下:1.采用分子动力学模拟的方法研究了单层黑磷在不同梯度温度下单轴(扶手椅型、锯齿型方向)、双轴(扶手椅型、锯齿型方向)拉伸时的力学性能。研究表明:单层黑磷在4.2K温度时沿扶手椅型、锯齿型方向单轴拉伸的杨氏模量分别为24GPa、105GPa,此结果与已有文献中采用第一性原理的计算结果能够很好的吻合。沿双轴拉伸的杨氏模量分别为22.6GPa、98.5GPa。无论在何种温度下单层黑磷沿锯齿型方向的杨氏模量均为沿扶手椅型方向的4.4倍,且随着温度的不断升高,两个方向的杨氏模量都在不断减小。此外,模拟计算得出单层黑磷在4.2K温度下沿扶手椅型、锯齿型两个方向拉伸时键长、键角以及离面角的变化,从侧面验证了模拟结果的准确性与模拟过程的严谨性。2.采用分子动力学模拟的方法研究了单层黑磷在不同梯度温度下纯剪切(扶手椅型、锯齿型方向)时的力学性能。研究表明:单层黑磷在4.2K温度时沿扶手椅型、锯齿型方向的剪切模量分别为25.4GPa、25.5GPa。无论在何种温度下,单层黑磷沿两个方向进行纯剪切时的剪切模量几乎相等,且随着温度的不断升高,其剪切模量在缓慢的减小。为了解释单层黑磷在纯剪切过程中的起皱行为,以4.2K温度时的模拟结果为例对其进行了理论分析,根据褶皱波长、振幅以及单层黑磷的泊松比、剪应变之间的关系将模拟结果与理论方法进行了对比,两者能够很好的吻合。3.采用分子动力学模拟的方法研究了单层黑磷纯弯曲时的力学性能。研究表明:单层黑磷沿扶手椅型、锯齿型方向纯弯曲时的弯曲刚度分别为6.5eV、8.8eV,此结果与已有文献中采用第一性原理计算的结果能够很好的吻合。此外结果还表明弯曲角度对单层黑磷弯曲刚度影响不显著。本文首次研究了单层黑磷在温度依赖下的力学性能,所得的模拟结果与理论结果可为黑磷力学性能的研究提供较好的理论支撑,为今后黑磷在工程中的应用也提供了一定的理论支撑与技术支撑。
文内图片：
图片说明：单层石墨烯平面结构示意图
[Abstract]:Black phosphorus, as a new two-dimensional material after graphene, has attracted the attention of researchers from all over the world because of its excellent optical and electrical properties. Black phosphorus is the most stable form of isomorphism of phosphorus, and its lattice is an orthogonal structure composed of several six rings connected with each other. Black phosphorus has just been discovered by scientists a few years ago. Now, the study of black phosphorus, a new two-dimensional material, has just started. There are few reports and studies on the electrical properties and mechanical properties of black phosphorus, especially at different temperatures. In view of the problems to be solved in the study of black phosphorus, the mechanical properties of monolayer black phosphorus under uniaxial tension and pure shear at 4.2K, 100K, 200K, 300K and 400K gradient temperatures were studied by molecular dynamics simulation. In addition, the mechanical properties of pure bending of monolayer black phosphorus were simulated and studied. The main research contents and results are as follows: 1. The mechanical properties of single layer black phosphorus under uniaxial (armchair type, sawtooth direction) and biaxial (armchair type, sawtooth direction) at different gradient temperatures were studied by molecular dynamics simulation. The results show that the Young's modulus of uniaxial tension of monolayer black phosphorus along armchair and sawtooth type at 4.2 K temperature is 24 GPA and 105 GPA, respectively. this result is in good agreement with the first principle calculation results in the literature. The Young's modulus of biaxial tension is 22.6GPA and 98.5GPA, respectively. At any temperature, the Young's modulus of monolayer black phosphorus in the direction of serrated type is 4.4 times higher than that in the direction of armchair type, and with the increase of temperature, the Young's modulus in both directions is decreasing. In addition, the changes of bond length, bond angle and off-surface angle of single-layer black phosphorus stretching along armchair and serrated shape at 4.2 K temperature are obtained, and the accuracy of the simulation results and the preciseness of the simulation process are verified from the side. 2. The mechanical properties of single layer black phosphorus in pure shear (armchair type, sawtooth direction) at different gradient temperatures were studied by molecular dynamics simulation. The results show that the shear modulus of single layer black phosphorus along armchair type and sawtooth type is 25.4GPA and 25.5GPA respectively at 4.2K temperature. At any temperature, the shear modulus of monolayer black phosphorus is almost equal when the pure shear is carried out in both directions, and the shear modulus decreases slowly with the increase of temperature. In order to explain the wrinkle behavior of monolayer black phosphorus in pure shear process, the simulation results at 4.2K temperature are taken as an example to analyze the wrinkle behavior of monolayer black phosphorus. According to the relationship between fold wavelength, amplitude, Poisson's ratio and shear strain of monolayer black phosphorus, the simulation results are compared with the theoretical method, and the simulation results are in good agreement with the theoretical method. The mechanical properties of monolayer black phosphorus under pure bending were studied by molecular dynamics simulation. The results show that the bending stiffness of single layer black phosphorus is 6.5 EV and 8.8 EV, respectively, when the single layer black phosphorus is bent in the direction of armchair and sawtooth type, which is in good agreement with the results calculated by the first principle in the literature. In addition, the results also show that the bending angle has no significant effect on the bending stiffness of single layer black phosphorus. In this paper, the mechanical properties of monolayer black phosphorus under temperature dependence are studied for the first time. The simulation results and theoretical results can provide good theoretical support for the study of mechanical properties of black phosphorus, and also provide certain theoretical support and technical support for the application of black phosphorus in engineering in the future.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.62
本文编号：2510098
文内图片：
图片说明：单层石墨烯平面结构示意图
[Abstract]:Black phosphorus, as a new two-dimensional material after graphene, has attracted the attention of researchers from all over the world because of its excellent optical and electrical properties. Black phosphorus is the most stable form of isomorphism of phosphorus, and its lattice is an orthogonal structure composed of several six rings connected with each other. Black phosphorus has just been discovered by scientists a few years ago. Now, the study of black phosphorus, a new two-dimensional material, has just started. There are few reports and studies on the electrical properties and mechanical properties of black phosphorus, especially at different temperatures. In view of the problems to be solved in the study of black phosphorus, the mechanical properties of monolayer black phosphorus under uniaxial tension and pure shear at 4.2K, 100K, 200K, 300K and 400K gradient temperatures were studied by molecular dynamics simulation. In addition, the mechanical properties of pure bending of monolayer black phosphorus were simulated and studied. The main research contents and results are as follows: 1. The mechanical properties of single layer black phosphorus under uniaxial (armchair type, sawtooth direction) and biaxial (armchair type, sawtooth direction) at different gradient temperatures were studied by molecular dynamics simulation. The results show that the Young's modulus of uniaxial tension of monolayer black phosphorus along armchair and sawtooth type at 4.2 K temperature is 24 GPA and 105 GPA, respectively. this result is in good agreement with the first principle calculation results in the literature. The Young's modulus of biaxial tension is 22.6GPA and 98.5GPA, respectively. At any temperature, the Young's modulus of monolayer black phosphorus in the direction of serrated type is 4.4 times higher than that in the direction of armchair type, and with the increase of temperature, the Young's modulus in both directions is decreasing. In addition, the changes of bond length, bond angle and off-surface angle of single-layer black phosphorus stretching along armchair and serrated shape at 4.2 K temperature are obtained, and the accuracy of the simulation results and the preciseness of the simulation process are verified from the side. 2. The mechanical properties of single layer black phosphorus in pure shear (armchair type, sawtooth direction) at different gradient temperatures were studied by molecular dynamics simulation. The results show that the shear modulus of single layer black phosphorus along armchair type and sawtooth type is 25.4GPA and 25.5GPA respectively at 4.2K temperature. At any temperature, the shear modulus of monolayer black phosphorus is almost equal when the pure shear is carried out in both directions, and the shear modulus decreases slowly with the increase of temperature. In order to explain the wrinkle behavior of monolayer black phosphorus in pure shear process, the simulation results at 4.2K temperature are taken as an example to analyze the wrinkle behavior of monolayer black phosphorus. According to the relationship between fold wavelength, amplitude, Poisson's ratio and shear strain of monolayer black phosphorus, the simulation results are compared with the theoretical method, and the simulation results are in good agreement with the theoretical method. The mechanical properties of monolayer black phosphorus under pure bending were studied by molecular dynamics simulation. The results show that the bending stiffness of single layer black phosphorus is 6.5 EV and 8.8 EV, respectively, when the single layer black phosphorus is bent in the direction of armchair and sawtooth type, which is in good agreement with the results calculated by the first principle in the literature. In addition, the results also show that the bending angle has no significant effect on the bending stiffness of single layer black phosphorus. In this paper, the mechanical properties of monolayer black phosphorus under temperature dependence are studied for the first time. The simulation results and theoretical results can provide good theoretical support for the study of mechanical properties of black phosphorus, and also provide certain theoretical support and technical support for the application of black phosphorus in engineering in the future.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.62
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