共查询到19条相似文献,搜索用时 140 毫秒
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利用密度泛函理论研究了NH3在完整和含有缺陷的硼纳米管上的吸附行为以及相关电子性质. 计算结果表明, 对于α硼纳米管, 在不同的直径和手性条件下, NH3均倾向于吸附在配位数为6的顶位上. 电子结构计算结果表明, NH3能够吸附在纳米管表面主要是由于N和B原子产生了较强的相互作用. 表明硼纳米管是一种潜在的NH3气气敏材料. 相似文献
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采用密度泛函理论研究了InnAsn (n≤90)管状团簇以及单壁InAs纳米管的几何结构、稳定性和电子性质. 小团簇InnAsn (n=1-3)基态结构和电子性质的计算结果与已有报道相一致. 当n≥4时优化得到了一族稳定的管状团簇, 其结构基元(In原子与As原子交替排列的四元环和六元环结构)满足共同的衍化通式. 团簇的平均结合能表明横截面为八个原子的管状团簇稳定性最好. 管状团簇前线轨道随尺寸的变化规律有效地解释了一维稳定管状团簇的生长原因, 同时也说明了实验上之所以能合成InAs纳米管的微观机理. 此外, 研究结果表明通过管状团簇的有效组装可得到宽带隙的InAs半导体单壁纳米管. 相似文献
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采用密度泛函理论(Density Functional Theory DFT)研究Au(100)和Au(111)表面含有不同Pd构型时表面的形成能.结果表明,非连续Pd构型的形成能较连续Pd构型的低,在表面易形成,其中第二临位Pd对构型被证实是乙烯与醋酸结合生成醋酸乙烯反应中催化活性最高的构型.随后计算CO在不同表面Pd原子的顶位吸附能和Pd原子的d带中心,结果显示表面Pd原子与相邻金原子之间几乎没有电子传递,并且PdAu(111)表面的Pd原子d带中心随周围Au原子个数的增加而远离费米能级,伴随着CO在其上吸附能的减小,但是同样的趋势在PdAu(100)表面不存在.最后,通过计算,CO在金属表面的吸附机理为CO成键轨道5σ的电子传递给Pd原子的d带,而Pd原子的d带电子又反馈回CO的反键轨道2π*. 相似文献
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采用密度泛函方法,构建了物理及化学吸附的羧基化碳纳米管,并优化一系列可能的构型,最终得到两种处理方式下的最稳定构型,对比及分析了构型的结构参数和电子分布。结果表明,羧基在碳纳米管表明发生物理吸附和化学吸附,将导致不同的杂化方式;当羧基以物理吸附的方式吸附在碳纳米管上时,其负电荷主要云集于羧基和吸附碳表面;当其以化学吸附的形式吸附在碳纳米管表面时,其负电荷则分散于碳纳米管表面以及吸附碳上。 相似文献
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通过卷曲二维锐钛矿(101)周期性单层片(sheets)构造了一系列不同手性((n,0), (0,m), (n,m))的一维单壁TiO2纳米管. 用周期性紧束缚密度泛函理论(DFTB)方法计算并比较了不同管径和手性的TiO2纳米管在几何结构、电子性质等方面的差别. 结果表明: 除了(6,0)管, 其余纳米管随着管径的增大, 应变能和能隙减小. 而在管径相同的情况下, 不同手性的(n,m)纳米管的应变能随着n/m的增加呈现先增大后减小的趋势, 能隙变化不大. 相似文献
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砷原子团簇结构的量子化学密度泛函理论研究 总被引:1,自引:0,他引:1
采用密度泛函理论的三种方法:局域自旋密度近似SVWN、梯度修正BLYP、杂化密度泛函B3LYP,优化了中性Asn、负离子Asn-(n=2~5)的结构,在优化结构基础上计算了它们的振动光谱,获得它们稳定的最低能量态的结构.其中中性Asn(n=2~5)的稳定结构的计算结果,与已有的理论结果以及实验数据进行了比较.而对负离子Asn-(n=2~5))的稳定结构作了预言.同时计算了Asn(n=2~5)的绝热电子亲和能(EAa),与有关光电子谱学的实验值符合较好. 相似文献
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运用广义梯度密度泛函理论的PW91方法结合周期平板模型,在DNP基组下研究了氧分子和氧原子在CuCl(111)表面上的吸附.对氧分子在CuCl(111)表面吸附的相关计算和比较发现,覆盖度为0.25单层时的吸附构型为稳定的吸附构型,氧分子倾斜地吸附在CuCl(111)表面的顶位时比较稳定,吸附后O2分子的伸缩振动频率与自由O2分子相比发生了红移.态密度和Mulliken电荷布居分析结果表明,整个吸附体系发生了由Cu原子向O2分子的电荷转移.氧原子在CuCl(111)表面吸附的计算结果表明,氧原子倾向于以穴位(hollow)吸附在CuCl(111)表面,通过Mulliken电荷布居和态密度分析对氧原子在CuCl表面的吸附行为作了进一步探讨. 相似文献
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First-Principles Study on Electronic and Optical Properties of Graphene-Like Boron Phosphide Sheets 下载免费PDF全文
Two-dimensional semiconducting materials with moderate band gap and high carrier mobil-ity have a wide range of applications for electronics and optoelectronics in nanoscale. On the basis of first-principles calculations, we perform a comprehensive study on the electronics and optical properties of graphene-like boron phosphide (BP) sheets. The global structure search and first-principles based molecular dynamic simulation indicate that two-dimensional BP sheet has a graphene-like global minimum structure with high stability. BP monolayer is semiconductor with a direct band gap of 1.37 eV, which reduces with the number of layers. Moreover, the band gaps of BP sheets are insensitive to the applied uniaxial strain.= The calculated mobility of electrons in BP monolayer is as high as 106 cm2/(V·s). Lastly, the MoS2/BP van der Waals heterobilayers are investigated for photovoltaic applications, and their power conversion efficiencies are estimated to be in the range of 17.7%-19.7%. This study implies the potential applications of graphene-like BP sheets for electronic and optoelectronic devices in nanoscale. 相似文献
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水分子和二氧化铈(111)表面相互作用的DFT+U研究 总被引:1,自引:0,他引:1
采用引入Hubbard参数U修正的密度泛函理论(DFT+U)方法, 对水分子在二氧化铈(111)表面的吸附作用进行了研究. 计算结果表明: 在氧化的二氧化铈(111)表面, 水分子以单氢键构型吸附在二氧化铈表面, 但是不能自发解离; 在还原的二氧化铈(111)表面, 水分子或化学吸附在衬底上, 或自发解离成表面羟基结构. 与氢气在氧化的二氧化铈(111)表面上物理吸附体系的总能相比, 羟基化表面构型是能量更低的构型, 所以羟基解离形成氢气, 从而使表面被氧化的过程需要有外部条件, 反应不能自发进行. 因此, 水分子在还原的二氧化铈(111)表面有两个可能的状态, 即无氢键结构的化学吸附和表面羟基结构的解离吸附. 在一定的外部条件下, 表面羟基结构进一步解离形成氢气, 并使还原的二氧化铈(111)表面得以氧化. 相似文献
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利用密度泛函方法对丙烯腈在Cu(111)面上不同吸附位的吸附状态进行了理论研究. 计算结果表明, 丙烯腈分子通过端位N原子立式吸附在金属铜表面为弱化学吸附, 其中桥位为较佳吸附位, 结合能为-40.16 kJ/mol; 丙烯腈分子和金属铜之间发生了电荷转移, N原子的孤对电子与金属形成σ共价键; 对丙烯腈分子结构变化进行了NBO分析, 解释了丙烯腈分子吸附后被活化的原因. 相似文献
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Poly(silanylenediethynylanthracene) (PSDEA) exhibits a hole-transporting ability experi-mentally. In order to simulate the property of PSDEA, a series of silanylenediethynylan-thracene oligomers were designed. The structures of these oligomers were optimized by using density function theory at B3LYP/6-31G(d) level. The energy gaps of the oligomers decrease with the increase in the chain length. The energy gaps of the oligomers also de-crease in the presence of the electron-withdrawing group on the anthracene ring. The 13C chemical shifts and nucleus independent chemical shifts (NICS) at the anthracene ring center in the oligomers were calculated at B3LYP/6-31G level. The chemical shifts of the carbon atoms connected with the nitryl group changed upfield, compared with those of the carbon atoms without the nitryl group. The aromaticity at the anthracene ring center decreases in the presence of the electron-withdrawing group, whereas increases with the increase in the number of the silanylene units. The most sensitive location for calculating the NICS values is 0.1 nm above the anthracene plane. 相似文献
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Imaging Molecular Orbitals of Single Picene Molecules Adsorbed on Cu(111) Surface: a Combined Experimental and Theoretical Study 下载免费PDF全文
Picene, which attracts the great interest of researchers, not only can be used to fabricate thin film transistors with high hole mobilities, but also is the parent material of a new type organic superconductor. Here, we investigate the electronic properties of individual picene molecules directly adsorbed on Cu(111) surface by a combination of experimental scanning tunneling microscopy/spectroscopy measurements and theoretical calculations based on the density functional theory. At low coverage, the picene molecules exhibit mono-dispersed adsorption behavior with the benzene ring planes parallel to the surface. The highest occupied state around-1.2 V and the lowest unoccupied state around 1.6 V with an obvious energy gap of the singly adsorbed picene molecule are identified by the dI/dV spectra and maps. In addition, we observe the strong dependence of the dI/dV signal of the unoccupied states on the intramolecular positions. Our first-principles calculations reproduce the above experimental results and interpret them as a specific molecule-substrate interaction and energy/spatial distributions of hybrid states mainly derived from different molecular orbitals of picene with some intermixing between them. This work provides direct information on the local electronic structure of individual picene on a metallic substrate and will facilitate the understanding the dependence of electron transport properties on the coupling between molecules and metal electrodes in single-molecule devices. 相似文献
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Electronic Structure and Circular Dichroism of Natural Alboatisins Isolated from Aerial Parts of Isodon Albopilosus: DFT and TDDFT Study 下载免费PDF全文
The stable conformations of a series of bioactive molecules, (?)-alboatisins A?C, are identified via Monte Carlo searching with the MMFF94 molecular mechanics force field. Then, the optical rotation (OR) values, vibrational circular dichroism (VCD), and electronic circular dichroism (ECD) spectra were calculated using the gradient-corrected density functional theory method. The vibrational and transition modes of molecular chirality were explored in terms of their microscopic origin. The calculated specific rotations are in agreement with the experimental values. From the OR analysis, it was concluded that optical rotation values areregulated by hydroxyl substitution. Vibrations occurring on the chiral skeleton may cause strong absorption in VCD spectra; VCD spectra are thus the spectral response to deformation vibrations on the chiral carbon skeleton. The lowest-energy negative Cotton effect is caused by σ→π* transition. Frontier molecular orbital analysis showed that strong ECD absorptions are produced when the dominant transition on the chiral skeleton is asymmetric; ECD spectra show the result of transitions lacking asymmetry on the chiral skeleton. 相似文献
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Ahmad Seif Temer S. Ahmadi Ali Bodaghi Javad Hosseini 《Journal of Molecular Structure》2009,911(1-3):19-23
The chemical shielding (CS) tensors of Gallium-71 and nitrogen-15 are computed for the first time in order to investigate the influence of Mn-doping on the electronic properties of the (5, 5) Gallium nitride nanotube (GaNNT). A GaNNT consisting of 40 Ga and 40 N atoms and having a 1.2 nm length was considered. One portal of the nanotube was capped by ten hydrogen atoms and other-end was kept open. Additionally, two other forms of this model of Mn-doped GaNNT were considered where a Mn-atom was substituted for a Ga atom either in the first or in the second layer. The calculations reveal that in both models of Mn-doped GaNNTs, the N atoms that are directly connected to the Mn atom have the smallest isotropic chemical shielding among other N atoms. These calculations were performed at the level of the density functional theory (DFT) using GAUSSIAN 03 package. The basis sets for Ga and N atoms were chosen to be 6-31G (d) and those for Mn atom were chosen to be LanL2DZ. 相似文献