In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-...In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-principles projector-augmented wave potential within the framework of density functional theory. The results show that the （4, 4） and （5, 5） tubes are too narrow to wrap a Cu chain, but the （6, 6） tube is nearly ideal to wrap a Cu chain on its centre axis. Wider tubes are anticipated to wrap more than one Cu chain spontaneously with forces amounting to a fraction of a nanonewton. Although the tube-chain interaction decreases with the increase of the tube diameter of （4, 4）, （5, 5） and （6, 6） successively, the charge density of the Cu@（6, 6） combined system still does not show complete superposition of that of the pristine （6, 6） tube and Cu chain. Successively reducing the restrictions of （4, 4）, （5, 5） and （6, 6） tubes on the Cu chain leads to a reduction in shift of the highest peak of the Cu chain towards lower energies, that is from -0.5177 eV of the isolated Cu chain to -1.36785 eV, -0.668 eV and -0.588 eV for the Cu@（4, 4）, Cu@（5, 5） and Cu@（6, 6） systems, respectively. In reverse, the strong metallic character of the Cu chain also enhances the metallic character of the combined systems so that the broader pseudogaps of the pristine carbon nanotubes around the Fermi level change into the narrow pseudogaps of the combined systems.展开更多
A supercell of a nanotube formed by a carbon nanotube (CNT) and a silicon nanotube (SiNT) is established. The electronic structure and optical properties are implemented through the first-principles method based on th...A supercell of a nanotube formed by a carbon nanotube (CNT) and a silicon nanotube (SiNT) is established. The electronic structure and optical properties are implemented through the first-principles method based on the density functional theory (DFT) with the generalized gradient approximation (GGA). The calculated results show that (6, 6) - (6, 6) silicon/carbon nanotubes (Si/CNTs) presented a direct band gap of 0.093 eV, (4, 4) - (6, 6) silicon/carbon nanotubes presented a direct band gap of 0.563 eV. The top of valence band was fundamentally determined by the Si-3p states and C-2p states, and the bottom of conduction band was primarily occupied by the C-2p states and Si-3p states in the Si/CNTs. It was found that (6, 6) - (6, 6) Si/CNTs have smaller energy band gap and better conductivity. Besides, Si/CNTs have satisfactory absorption characteristics and luminous efficiency in ultraviolet band.展开更多
Based on first-principle calculations, the electronic structures and optical properties of a single-walled （7, 0） SiC nanotube （SiCNT） with a carbon vacancy defect or a silicon vacancy defect are investigated. In ...Based on first-principle calculations, the electronic structures and optical properties of a single-walled （7, 0） SiC nanotube （SiCNT） with a carbon vacancy defect or a silicon vacancy defect are investigated. In the three silicon atoms around the carbon vacancy, two atoms form a stable bond and the other is a dangling bond. A similar structure is found in the nanotube with a silicon vacancy. A carbon vacancy results in a defect level near the top of the valence band, while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube. Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.展开更多
Binding energies and geometrical and electronic structures for adsorptions of CO and NO on metal M(Pd or Pt)loaded or M and di-vacancy co-decorated(5,5)single-walled carbon nanotubes(M-CNTs or M-V2-CNTs)are studied us...Binding energies and geometrical and electronic structures for adsorptions of CO and NO on metal M(Pd or Pt)loaded or M and di-vacancy co-decorated(5,5)single-walled carbon nanotubes(M-CNTs or M-V2-CNTs)are studied using a GGA-PBE method in the work.The calculated results show that the di-vacancy defect in a perfect(5,5)tube opens the band gap,makes the(5,5)tube transform from a conductor into a semiconductor,and strengthens the adsorption of metal M on the(5,5)tube.For the adsorptions of CO and NO on M-CNT and M-V2-CNT,the CO and NO molecules can be both chemically adsorbed on loaded Pd or Pt atoms due to their active adsorption sites.NO is easily adsorbed on M-V2-CNT because of its electron configuration with a high 2p energy level and its adsorption significantly changes the band gap of M-V2-CNT and makes M-V2-CNT transform from a semiconductor to a conductor.However,the adsorption of CO can not cause the conductivity of M-V2-CNT change.M-V2-CNT has a good sensitivity to the NO gas,suitable as a sensor for detecting the NO gas molecule.In addition,the existence of di-vacancy defect decreases the interaction between CO or NO and Pt-CNT,which will contribute to the desorption of CO and NO gases.The work is expected to provide a theoretical basis for designing NO sensing devices.展开更多
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2004CB619302)
文摘In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-principles projector-augmented wave potential within the framework of density functional theory. The results show that the （4, 4） and （5, 5） tubes are too narrow to wrap a Cu chain, but the （6, 6） tube is nearly ideal to wrap a Cu chain on its centre axis. Wider tubes are anticipated to wrap more than one Cu chain spontaneously with forces amounting to a fraction of a nanonewton. Although the tube-chain interaction decreases with the increase of the tube diameter of （4, 4）, （5, 5） and （6, 6） successively, the charge density of the Cu@（6, 6） combined system still does not show complete superposition of that of the pristine （6, 6） tube and Cu chain. Successively reducing the restrictions of （4, 4）, （5, 5） and （6, 6） tubes on the Cu chain leads to a reduction in shift of the highest peak of the Cu chain towards lower energies, that is from -0.5177 eV of the isolated Cu chain to -1.36785 eV, -0.668 eV and -0.588 eV for the Cu@（4, 4）, Cu@（5, 5） and Cu@（6, 6） systems, respectively. In reverse, the strong metallic character of the Cu chain also enhances the metallic character of the combined systems so that the broader pseudogaps of the pristine carbon nanotubes around the Fermi level change into the narrow pseudogaps of the combined systems.
文摘A supercell of a nanotube formed by a carbon nanotube (CNT) and a silicon nanotube (SiNT) is established. The electronic structure and optical properties are implemented through the first-principles method based on the density functional theory (DFT) with the generalized gradient approximation (GGA). The calculated results show that (6, 6) - (6, 6) silicon/carbon nanotubes (Si/CNTs) presented a direct band gap of 0.093 eV, (4, 4) - (6, 6) silicon/carbon nanotubes presented a direct band gap of 0.563 eV. The top of valence band was fundamentally determined by the Si-3p states and C-2p states, and the bottom of conduction band was primarily occupied by the C-2p states and Si-3p states in the Si/CNTs. It was found that (6, 6) - (6, 6) Si/CNTs have smaller energy band gap and better conductivity. Besides, Si/CNTs have satisfactory absorption characteristics and luminous efficiency in ultraviolet band.
基金Project supported by the China Postdoctoral Science Foundation(No.201104619)the Fund of Shaanxi Provincial Educational Department (No.2010JK775)
文摘Based on first-principle calculations, the electronic structures and optical properties of a single-walled （7, 0） SiC nanotube （SiCNT） with a carbon vacancy defect or a silicon vacancy defect are investigated. In the three silicon atoms around the carbon vacancy, two atoms form a stable bond and the other is a dangling bond. A similar structure is found in the nanotube with a silicon vacancy. A carbon vacancy results in a defect level near the top of the valence band, while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube. Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.
基金the National Natural Science Foundation(No.51474133)Inner Mongolia Natural Science Foundation(No.2016MS0513)。
文摘Binding energies and geometrical and electronic structures for adsorptions of CO and NO on metal M(Pd or Pt)loaded or M and di-vacancy co-decorated(5,5)single-walled carbon nanotubes(M-CNTs or M-V2-CNTs)are studied using a GGA-PBE method in the work.The calculated results show that the di-vacancy defect in a perfect(5,5)tube opens the band gap,makes the(5,5)tube transform from a conductor into a semiconductor,and strengthens the adsorption of metal M on the(5,5)tube.For the adsorptions of CO and NO on M-CNT and M-V2-CNT,the CO and NO molecules can be both chemically adsorbed on loaded Pd or Pt atoms due to their active adsorption sites.NO is easily adsorbed on M-V2-CNT because of its electron configuration with a high 2p energy level and its adsorption significantly changes the band gap of M-V2-CNT and makes M-V2-CNT transform from a semiconductor to a conductor.However,the adsorption of CO can not cause the conductivity of M-V2-CNT change.M-V2-CNT has a good sensitivity to the NO gas,suitable as a sensor for detecting the NO gas molecule.In addition,the existence of di-vacancy defect decreases the interaction between CO or NO and Pt-CNT,which will contribute to the desorption of CO and NO gases.The work is expected to provide a theoretical basis for designing NO sensing devices.
