常规及非常规碳纳米管径向稳定性与构型转换

发布时间：2018-02-09 07:27

本文关键词： 碳纳米管分子力学径向稳定性坍塌活化能　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：碳纳米管作为一种新型的纳米材料,具有很好的力学、电学、化学等性能,在许多领域有着广泛的应用前景,自发现以来受到人们越来越广泛的关注。尤其是碳纳米管具有中空的结构和光滑的表面,其可作为药物、流体及低维纳米材料等的一种理想的传输通道和储存装置。然而碳纳米管的传输效力和存储能力与其结构稳定性密切相关,因此开展具有不同手性和尺寸的碳纳米管的稳定性相关实验、理论及数值模拟研究具有重要的科学意义和实用价值。本文从分子力学模拟角度出发,研究了常规和非常规碳纳米管的结构径向稳定性及构型转换,分析了手性、半径及壁数对径向稳定性的影响,获得了构型转换活化能与碳纳米管半径之间的关系,主要工作包括：常规单壁、双壁及三壁碳纳米管的径向稳定性及构型转换研究。基于分子力学模拟获得了常规碳纳米管径向未坍塌及坍塌稳定构型,基于NEB方法分析了单壁、双壁及三壁碳纳米管从未坍塌到坍塌构型转换的最低能量路径及活化能,进一步分析了结构径向坍塌与碳管的手性和半径之间的关系。研究结果表明：1)碳纳米管向坍塌构型转换所需的活化能随碳管半径的增大而减小,半径较大的碳纳米管更易坍塌；2)锯齿型碳纳米管向坍塌构型转换所需的活化能略低于扶手椅型碳纳米管向坍塌构型转换所需的活化能；3)内管半径相近且与单壁碳纳米管半径相当时,碳纳米管坍塌活化能随着壁数的增加而增加。非常规双壁及三壁碳纳米管的径向稳定性及构型转换研究。基于已有文献结果,构造了非常规双壁及三壁碳纳米管未坍塌构型,通过分子力学模拟获得了非常规碳纳米管的径向坍塌稳定构型,并结合NEB方法获得了构型转换的最低能量路径与活化能,分析了非常规碳纳米管径向坍塌与管手性及半径之间的关系。研究结果表明：1)当内管半径较小时,内管不易发生坍塌且主要以缺陷的形式存在,其将导致非常规碳纳米管向坍塌构型转换所需的活化能随内管半径的增加而减小；2)随着内管半径的增大,内管主要起支撑的作用,因此非常规碳纳米管向坍塌构型转换所需的活化能随内管半径的增大而增加。本文研究工作为进一步理解碳纳米管的径向稳定性提供了理论依据,也为碳纳米管在传输通道和储存装置中的应用及其结构稳定性提供了理论指导。
[Abstract]:Carbon nanotubes (CNTs), as a new type of nanomaterials, have good mechanical, electrical and chemical properties, and have a wide range of applications in many fields. Carbon nanotubes, in particular, have hollow structures and smooth surfaces, which can be used as drugs. An ideal transport channel and storage device for fluid and low-dimensional nanomaterials, however, the transport efficiency and storage capacity of carbon nanotubes are closely related to their structural stability. Therefore, it is of great scientific significance and practical value to study the stability of carbon nanotubes with different chiral properties and sizes in theory and numerical simulation. The structure radial stability and configuration conversion of conventional and unconventional carbon nanotubes are studied. The effects of chirality, radius and wall number on radial stability are analyzed. The relationship between the configuration conversion activation energy and the radius of carbon nanotubes is obtained. The main work includes: the radial stability and configuration transformation of conventional single-walled, double-walled and three-walled carbon nanotubes. Based on molecular mechanics simulation, the radial uncollapsed and collapsing stable configurations of conventional carbon nanotubes are obtained, and the single wall is analyzed based on NEB method. The lowest energy path and activation energy of the two-wall and three-walled carbon nanotubes that never collapse into the collapse configuration transition, The relationship between the radial collapse of the structure and the chirality and radius of the carbon tube is further analyzed. The results show that the activation energy required for the transition of the carbon nanotube to the collapse configuration decreases with the increase of the radius of the carbon tube. Carbon nanotubes with larger radius are more likely to collapse.) the activation energy required for the conversion of sawtooth carbon nanotubes to collapse configurations is slightly lower than the activation energy required for the transition from armchair carbon nanotubes to collapse configurations. The inner tube radius is similar to that of single-walled carbon tubes. When the radius of nanotubes is equal, The activation energy of collapse of carbon nanotubes increases with the increase of the number of walls. The radial stability and configuration transformation of unconventional double-walled and three-walled carbon nanotubes are studied. Based on the results of previous literatures, the uncollapsed configurations of unconventional double-walled and three-walled carbon nanotubes are constructed. The radial collapse stable configuration of unconventional carbon nanotubes was obtained by molecular mechanics simulation, and the lowest energy path and activation energy of configuration conversion were obtained by NEB method. The relationship between the radial collapse of unconventional carbon nanotubes and the chirality and radius of the tubes is analyzed. The results show that when the radius of the inner tubes is small, the inner tubes are not easy to collapse and mainly exist in the form of defects. The activation energy required for the transition of the unconventional carbon nanotubes to the collapse configuration decreases with the increase of the inner tube radius.) with the increase of the inner tube radius, the inner tube plays a supporting role. Therefore, the activation energy required for the transition from unconventional carbon nanotubes to collapsing configurations increases with the increase of the radius of the inner tubes. This work provides a theoretical basis for further understanding the radial stability of carbon nanotubes. It also provides theoretical guidance for the application and structural stability of carbon nanotubes in transport channels and storage devices.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O613.71

【参考文献】