Stone–Wales(SW) defects are possibly formed in graphene and other two-dimensional materials, and have multiple influence on their physical and chemical properties. In this study, the transition state of SW defects in...Stone–Wales(SW) defects are possibly formed in graphene and other two-dimensional materials, and have multiple influence on their physical and chemical properties. In this study, the transition state of SW defects in graphene is determined with the fully discrete Peierls theory. Furthermore, the atomic formation process is investigated by means of ab-initio simulations. The atomic structure change and energetics of the SW transformation are revealed. It is found that the transition state is at the SW bond rotation of 34.5°and the activation energy barrier is about 12 eV. This work provides a new method to investigate SW transformations in graphene-like materials and to explore unknown SW-type defects in other 2D materials.展开更多
The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） ar...The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） are compared with perfect tubes. The influences of type and concentration of the defect, length, diameter, and chirality of the tube, and the ambient temperature are taken into consideration. It is demonstrated that defects result in a dramatic reduction of thermal conductivity. Doping and Stone-Wales （SW） defects have greater effect on armchair tubes, while vacancy affects the zigzag ones more. Thermal conductivity of the nanotubes increases, reaches a peak, and then decreases with increasing temperature. The temperature at which the thermal conductivity peak occurs is dependent on the defect type. Different from SW or vacancy tubes, doped tubes are similar to the perfect ones with a sharp peak at the same temperature. Thermal conductivity goes up when the tube length grows or diameter declines. It seems that the length of thermal conductivity convergence for SW tubes is much shorter than perfect or vacancy ones. The SW or vacancy tubes are less sensitive to the diameter change, compared with perfect ones.展开更多
By employing atomistic simulations based on an empirical potential model and a self-consistent-charge density-functional tight-binding method, the collision dynamics process of an energetic carbon ion impinging on the...By employing atomistic simulations based on an empirical potential model and a self-consistent-charge density-functional tight-binding method, the collision dynamics process of an energetic carbon ion impinging on the Stone-Wales defect in a single-walled carbon nanotube was investigated. The outwardly and inwardly displacement threshold energies for the primary knock-on atom in the Stone-Wales defect were calculated to be 24.0 and 25.0 eV, respectively. The final defect configuration for each case was a 5-1DB-T（DB=dangling bond） defect formed in the front surface of the nanotube. Moreover, the minimum incident energy of the projectile prompting the primary knock-on atom displacement was predicted to be 71.0 eV, and the time evolutions of the kinetic and potential energies of the projectile and the primary knock-on atom were both plotted to analyze the energy transfer process.展开更多
Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification s...Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification stage or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this article, mechanical properties of single-walled nanotubes with defects are studied under both compressive and tensile loads using molecular dynamics （MD） simulations. Two types of defectStone-Wales and vacancy defects with different defect densities are considered for present investigation. Molecular simulations are carried out using the classical MD method. The Brenner potential is used for carbon-carbon interaction in the CNT. Temperature of the system is controlled by velocity scaling. Simulation results show that the defects have negligible effect on the modulus of elasticity of nanotubes. However, they have significant effect on the failure stress and strain of the nanotubes.展开更多
采用密度泛函理论中的UB3LYP方法,研究了石墨烯中的Stone-wales缺陷对铂原子催化解离氧气分子的影响.通过计算发现,氧气分子在以Stone-wales缺陷石墨烯片为载体的铂上(Pt-SW)形成3种吸附结构,通过4条路径,最终生成两种产物.氧气分子最...采用密度泛函理论中的UB3LYP方法,研究了石墨烯中的Stone-wales缺陷对铂原子催化解离氧气分子的影响.通过计算发现,氧气分子在以Stone-wales缺陷石墨烯片为载体的铂上(Pt-SW)形成3种吸附结构,通过4条路径,最终生成两种产物.氧气分子最易通过[2+1]环加成作用,吸附在以Stone-wales缺陷石墨烯片为载体的Pt的表面上,吸附能(Eads)为-0.64eV.由于石墨烯片上的Stone-wales缺陷的存在,氧气分子在Pt-SW上解离的4条路径中最有利的解离路径中的决速步能垒都明显高于氧气在以完美石墨烯为载体的Pt(Pt/Graphene)上解离的能垒(1.51eV vs 1.35eV),相应吸收的热量也高于在Pt/Graphene上吸收的热量(0.79eVvs0.15eV).展开更多
Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buck...Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated.MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube.The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall,and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect.It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one.The harmful effects of defects do not depend simply on the size of the defective area,but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 11847089)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 20KJB430002)GuiZhou Provincial Department of Science and Technology, China (Grant No. QKHJC[2019]1167)。
文摘Stone–Wales(SW) defects are possibly formed in graphene and other two-dimensional materials, and have multiple influence on their physical and chemical properties. In this study, the transition state of SW defects in graphene is determined with the fully discrete Peierls theory. Furthermore, the atomic formation process is investigated by means of ab-initio simulations. The atomic structure change and energetics of the SW transformation are revealed. It is found that the transition state is at the SW bond rotation of 34.5°and the activation energy barrier is about 12 eV. This work provides a new method to investigate SW transformations in graphene-like materials and to explore unknown SW-type defects in other 2D materials.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50876010 and 51176011)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-08-0721)
文摘The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） are compared with perfect tubes. The influences of type and concentration of the defect, length, diameter, and chirality of the tube, and the ambient temperature are taken into consideration. It is demonstrated that defects result in a dramatic reduction of thermal conductivity. Doping and Stone-Wales （SW） defects have greater effect on armchair tubes, while vacancy affects the zigzag ones more. Thermal conductivity of the nanotubes increases, reaches a peak, and then decreases with increasing temperature. The temperature at which the thermal conductivity peak occurs is dependent on the defect type. Different from SW or vacancy tubes, doped tubes are similar to the perfect ones with a sharp peak at the same temperature. Thermal conductivity goes up when the tube length grows or diameter declines. It seems that the length of thermal conductivity convergence for SW tubes is much shorter than perfect or vacancy ones. The SW or vacancy tubes are less sensitive to the diameter change, compared with perfect ones.
基金Supported by the National Natural Science Foundation of China（Nos. 11505003, 11505092）, the Natural Science Foundation of Anhui Province, China（No. 1608085 QA20）, the Postdoctoral Science Foundation of Anhui Province, China（No.2016B091） and the Introduced Doctor＇s Startup Fund from Anhui University of Science and Technology, China（No.ZX944）.
文摘By employing atomistic simulations based on an empirical potential model and a self-consistent-charge density-functional tight-binding method, the collision dynamics process of an energetic carbon ion impinging on the Stone-Wales defect in a single-walled carbon nanotube was investigated. The outwardly and inwardly displacement threshold energies for the primary knock-on atom in the Stone-Wales defect were calculated to be 24.0 and 25.0 eV, respectively. The final defect configuration for each case was a 5-1DB-T（DB=dangling bond） defect formed in the front surface of the nanotube. Moreover, the minimum incident energy of the projectile prompting the primary knock-on atom displacement was predicted to be 71.0 eV, and the time evolutions of the kinetic and potential energies of the projectile and the primary knock-on atom were both plotted to analyze the energy transfer process.
基金support of this research by the DAERS division of Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
文摘Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification stage or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this article, mechanical properties of single-walled nanotubes with defects are studied under both compressive and tensile loads using molecular dynamics （MD） simulations. Two types of defectStone-Wales and vacancy defects with different defect densities are considered for present investigation. Molecular simulations are carried out using the classical MD method. The Brenner potential is used for carbon-carbon interaction in the CNT. Temperature of the system is controlled by velocity scaling. Simulation results show that the defects have negligible effect on the modulus of elasticity of nanotubes. However, they have significant effect on the failure stress and strain of the nanotubes.
文摘采用密度泛函理论中的UB3LYP方法,研究了石墨烯中的Stone-wales缺陷对铂原子催化解离氧气分子的影响.通过计算发现,氧气分子在以Stone-wales缺陷石墨烯片为载体的铂上(Pt-SW)形成3种吸附结构,通过4条路径,最终生成两种产物.氧气分子最易通过[2+1]环加成作用,吸附在以Stone-wales缺陷石墨烯片为载体的Pt的表面上,吸附能(Eads)为-0.64eV.由于石墨烯片上的Stone-wales缺陷的存在,氧气分子在Pt-SW上解离的4条路径中最有利的解离路径中的决速步能垒都明显高于氧气在以完美石墨烯为载体的Pt(Pt/Graphene)上解离的能垒(1.51eV vs 1.35eV),相应吸收的热量也高于在Pt/Graphene上吸收的热量(0.79eVvs0.15eV).
基金the National Natural Science Foundation of China(No.11272123)the China Postdoctoral Science Foundation(No.2011M500132)+1 种基金the Fundamental Research Funds for the Central UniversitiesSouth China University of Technology (No.2012ZB0023)
文摘Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated.MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube.The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall,and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect.It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one.The harmful effects of defects do not depend simply on the size of the defective area,but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.
