碳掺杂闭口硼氮纳米管场发射第一性原理研究

运用第一性原理研究了闭口硼氮纳米管（BNNT）顶层掺碳体系（C@BNNT）的电子场发射性能.结果表明：随外电场增强,C@BNNT电子结构变化显著,态密度（DOS）向低能方向移动;碳原子的局域态密度（LDOS）在费米能级附近明显增大;赝能隙、最高占据分子轨道（HOMO）/最低未占据分子轨道（LUMO）能隙减小;体系电荷移向帽端.DOS,HOMO/LUMO及Mulliken电荷分析一致表明,与BNNT相比,C@BNNT电子场发射性能显著改善,且C@BN_moreNT性能更优. 关键词： 碳掺杂 硼氮纳米管 电子场发射 第一性原理     

碳掺杂硼氮纳米管电子场发射的第一性原理研究

对闭口硼氮纳米管（BNNT）顶层掺碳体系,运用第一性原理研究了电子场发射性能.结果表明,掺碳的BNNT体系电子结构变化显著;外电场愈强,体系态密度向低能端移动幅度愈大,且最高占据分子轨道（HOMO）/最低未占据分子轨道（LUMO）能隙愈小.体系态密度和局域态密度,HOMO和LUMO及其能隙分析一致表明,各种碳掺杂体系中C_eqBNNT的场发射性能最佳. 关键词： 硼氮纳米管 碳掺杂 第一性原理     

氮掺杂及水分子吸附碳纳米管电子场发射第一性原理研究

对闭口碳纳米管(CNT)顶端分层掺氮及吸附不同数目水分子体系,运用第一性原理研究了有电场存在时的电子场发射性能.结果表明：掺氮并吸附水分子的CNT结构稳定;外电场愈强、水分子数愈多,体系态密度(DOS)向低能端移动幅度愈大且最高分子占据轨道(HOMO)/最低分子空轨道(LUMO)能隙愈小.吸附能,DOS/LDOS,HOMO/LUMO及其能隙分析一致表明,第三层氮掺杂CNT吸附不同数目水分子体系的场发射性能最佳. 关键词： 氮掺杂 水吸附 密度泛函理论 电子场发射     

碳纳米锥电子场发射的第一性原理研究

运用第一性原理研究了不同锥角和结构的碳纳米锥 （CNC） 电子场发射性能.结果表明：随外电场 （E_add） 增强,CNC电子结构变化显著,费米能级 （E_f） 处态密度 （DOS） 明显增大;赝能隙减小;体系电荷移向尖端.DOS,HOMO/LUMO及Mulliken电荷分析表明：CNC的电子场发射性能除依赖于尖端结构外,很大程度上还取决于锥角大小,特别顶层6个原子的CNC₃和CNC₄场发射性能 关键词： 碳纳米锥 电子场发射 第一性原理     

Sc12X团簇(X=B,C,N,Al,Si,P)的电子结构和稳定性

基于第一性原理,在密度泛函理论框架下,用广义梯度近似(GGA)研究二十面体Sc12X(X=B、C、N、Al、Si、P)中性和荷电团簇的电子结构和稳定性,系统计算了它们的基态束缚能(BE)、原子间平衡间距、最高占据轨道(HOMO)与最低占据轨道(LUMO)之间的能隙、局域电荷以及HOMO电子构型.研究表明,用C、Si原子或荷电后的B、N、Al、P离子分别替代团簇Sc13中心原子可以使其成为稳定的结构.Sc12X团簇束缚能改变的原因在于掺杂改变了中心原子或离子与表面原子的轨道杂化.     

掺硼水吸附碳纳米管电子场发射性能的第一性原理研究

运用第一性原理研究了掺硼碳纳米管(BCNT)顶端吸附水分子后的电子场发射性能.结果表明：掺B及吸附H₂O的碳纳米管(BCNT+H₂O)端部形成电子聚集的原子尺度微区,其电子态密度(DOS)在费米能级(E_f)附近有很大提高.根据计算的电子DOS,HOMO/LUMO及Mulliken电荷分布等可知BCNT+H₂O比CNT+H₂O有更好的场发射性能. 关键词： 掺硼碳纳米管 吸附 密度泛函理论 电子场发射     

TPD/PBD界面电致激基复合物几何结构和 电子结构的理论

利用第一性原理对由TPD⁺和PBD^-形成的电致激基复合物(TPD⁺PBD^-)进行基于密度泛函的能量、轨道等性质的计算。结果表明:界面处离子态的TPD⁺ 和 PBD^-更易形成处于更低能量状态的电致激基复合物。几何结构的数据分析表明:电致激基复合物(TPD⁺PBD^-)是电子从PBD^-转移至TPD⁺形成的电荷转移态;电致激基复合物的最低空轨道(LUMO)定域在电致激基复合物PBD^- 的一侧;它的最高占据轨道(HOMO)定域在电致激基复合物TPD⁺的一侧;且前线分子轨道无重叠。电致激基复合物的能隙为1.3 eV,与PBD 的LUMO到TPD的HOMO的能级差1.6 eV相近。在理论上说明了电致激基复合物的发光是从PBD的LUMO到TPD的HOMO的电子跃迁。     

金基纳米管AunSi12 (n=25-60)的奇异结构与电磁特性预测

应用相对论效应的密度泛函理论,系统研究了一系列稳定的中空类管状Au_nSi₁₂(n=25, 30, 35, 40, 45, 50, 55, 60)团簇. Au_nSi₁₂可以通过在不同长度的单壁Au纳米管(5, 5)的两端戴帽由二十面体Au₂₀Si₁₂平分的两个相同半球构建而成.计算结果显示,Si原子的掺杂使得Au_nSi₁₂的结构变得更加紧密且加强了相应的类管状Au团簇的稳定性.最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)之间的能隙值在0.041 eV至0.138 eV区间,表明Au_nSi₁₂具有较高的化学活性.电子结构分析显示,Si原子和Au原子之间的p-d轨道杂化在形成和维持Au_nSi₁₂的类管状结构方面发挥了重要作用.Hirshfeld电荷分析显示,电荷从Au原子转移到Si原子上,Au_n...     

第一性原理研究电场对BN纳米管电子结构的影响

采用基于密度泛函理论的第一性原理计算研究了电场对BN纳米管的电子结构的影响.首先对在不同电场强度下的纳米管几何结构进行了优化,可以看出纳米管沿轴方向层间距出现了不规则的变化.电子能带结构显示,在电场作用下,zigzag型和armchair型两种结构纳米管的能带向低能方向移动,并且导致纳米管的带隙有显著的减小.电场使得armchair型纳米管的带隙发生了从间接带隙向直接带隙的转变.在电场作用下,纳米管的两端态密度呈现出明显的差异,正负电荷沿轴向出现了沿轴向的空间分离,Mulliken电荷分布图揭示出最高占据轨道和最低未占据轨道分居在纳米管的两端.     

Matlab编程的Hückel分子轨道法计算研究掺杂纳米碳管的化学反应性（英文）

使用Matlab自编简单Hückel分子轨道法(SHMO)计算程序,分析空位、Stone-Wales缺陷位、N和B原子掺杂的CNT(5,5)碳纳米管,计算π电子密度和前线分子轨道(HOMO和LUMO)为研究掺杂相对碳纳米管的化学反应性提供依据.具有不同电特性的掺杂相打破了碳纳米管的π电子、HOMO和LUMO的均衡分布.掺杂相和/或邻近的碳原子为HOMO或LUMO贡献了较其它原子更大的轨道系数,在不同的化学反应中表现出良好的亲核性或亲电性.此外,HOMO-LUMO能量差很好地反映了掺杂纳米碳管的导电性.计算结果与已报道的实验和理论结果吻合良好.     

Theoretical investigation on the oligothienoacenes under the influence of external electric field

Theoretical investigation on a series of oligothienoacenes has been carried out at the B3LYP/6-31G* level by considering the influence of the external electric field. With the electric field increasing, the carbon-carbon single bonds become shorter and the carbon-carbon double bonds become longer, resulting in a better conjugation. Due to the different electron density, the charge mobility of the sulfur is more obvious than that of the carbon. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap decreases with the EF intensity increasing. The applied EF also changes the spatial distribution of the molecular orbits: LUMO and several higher orbitals shift to the high potential side, whereas HOMO and several lower ones shift to the low potential side. All these features behave more pronounced with increasing conjugated chain length.     

Ab initio study for structure, electric properties and light emission of linear-trans-quinacridone

The structure, electric properties and emission rate of linear-trans-quinacridone are investigated within the density functional theory (DFT) calculations. We find the structure of the molecule to be planar with an energy gap of 3.06 eV. The emission lifetime from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) of this material is found to be 24 ns, which is in good agreement with experimental results.     

DFT and ab initio study on non-linear optical (NLO) properties of some organic complexes with different conjugate linker and substituent groups

A series of Schiff-bases chromophores containing imine or double C=C bond linkers between the donor and acceptor have been studied by first-principles calculations. The molecular structures, electronic properties and second order nonlinearities were investigated by DFT and ab initio methods. The optimized structural parameters of these Schiff-base derivates showed that these compounds are stable. The results of TD-DFT calculations indicate that the derivatives with the heterocyclic and imine linker have a red shift absorption compared to derivatives with the double C=C or N=N bonds. The analysis of the frontier molecular orbitals indicates that the CN group and the heterocycle linked by the CN or imine group has contribution to the LUMO orbital while the groups N(CH₃)₂ and the benzene ring linked by the double C=C or N=N bond have contribution to the HOMO orbital. The CN and the heterocyclic acceptors enable the derivatives to have a larger first static hyperpolarizability. However, the compounds 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-pyridin-1-yl}-propanel-1-sulfonoperoxoic acid and 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-quinolin-1-yl}propanel-1-sulfonoperoxoic acid with a substituent also have large first static hyperpolarizabilities due to the overwhelming contributions of electron density of the group to the HOMO orbital, that is, the HOMO orbital were constituted by the SO ₃ ^? group only. In order to understand the influence of the energy gap (??E) between the HOMO and the LUMO orbitals on the first static hyperpolarizability, we calculated the energy gap (??E) of all Schiff-base compounds. The results show that the smaller the HOMO-LUMO energy gap the larger the first static hyperpolarizability. The present study demonstrated that these compounds which have pure C=N double bond and heterocyclic substitution groups may have potential applications in the development of NLO materials.     

Synthesis and Properties of Diphenylcarbazole Triphenylethylene Derivatives with Aggregation-Induced Emission, Blue Light Emission and High Thermal Stability

New aggregation-induced emission materials derived from diphenylcarbazole triphenylethylene were prepared. The thermal, photophysical, electrochemical and aggregation-induced emissive properties were investigated. All the compounds had strong blue light emission capability and excellent thermal stability. Their maximum fluorescence emission wavelengths were between 450 to 460 nm in TLC plates, while their glass transition temperatures ranged from 162.2 to 182.4 °C. The decomposition temperatures of the synthesized compounds were all well over 500 °C. The synthesized compounds possessed aggregation-induced emission (AIE) properties, which exhibited enhanced fluorescence emissions in aggregation states or in solid states. The HOMO energy levels estimated from the oxidation potentials were found in the range from 5.49 to5.52 eV. The lowest unoccupied molecular orbital/highest occupied molecular orbital (LUMO/HOMO) energy gaps (ΔEg) for the compounds were estimated from the onset absorption wavelengths of UV absorption spectra and ranged from 3.04 to 3.20 eV.