On the production of excited hydroxyl radicals in the H+O3-atomic flame

The existence of surface states in band gaps of a nearly free electron band structure is investigated. While in gaps at the Brillouin zone boundary one finds such a state only for positive potential matrix element, there a surface state always exists for band gaps inside the Brillouin zone.     

Effect of boron and nitrogen co-doping on CNT's electrical properties: Density functional theory

In this work, we have theoretically studied the changes in electrical properties of three different geometrical structures of carbon nanotubes upon co-doping them with boron and nitrogen atoms. We applied different doping mechanisms to study band structure variations in the doped structures. Doping carbon nanotubes with different atoms will create new band levels in the band structure and as a consequence, a shift in the Fermi level occurs. Whereas, filling up the lowest conduction/ upper valence bands created an up/ downshift in the Fermi level. Moreover, dopants concentration and dopants position play a critical rule in defining the number of new band levels. These new band levels in the band gap region represented as new peaks appeared in the density of states. These new bands are solely attributed to co-doping carbon nanotubes with boron and nitrogen atoms.     

Anomalous magnetotransport in chemically doped carbon nanotubes

We report on anomalous magnetotransport features in chemically doped, weakly disordered carbon nanotubes. Under the application of a magnetic field parallel to the tube axis, hole conduction is shown to be strongly affected by impurity scattering with short mean free path and negative magnetoresistance, strongly different from electron conduction with much longer mean free path and positive magnetoresistance behavior.     

Design of soliton electron lattices in carbon nanotubes by a magnetic field

Electron states in the conduction band of carbon nanotubes are studied in the presence of a constant magnetic field perpendicular to the tube axis within the framework of Hubbard's model. Numerical solutions describing electron density waves corresponding to soliton lattices are obtained. The possibility of control over the electron lattice parameters with the help of a constant magnetic field is established. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 17–23, December, 2008.     

扶手椅型碳化硅纳米管电子结构和光学性质的研究

本文基于密度泛函理论研究了扶手椅型碳化硅纳米管(SiCNT)的电子结构、成键机制以及其光学性质。研究结果表明:当碳和硅的原子比为1∶1时,SiCNT的结构最为稳定,并且表现出诸多的优良性质。通过分析计算结果我们发现,SiCNT是间接带隙材料,并且管子的带隙随着直径的增加而增加。从SiCNT的轨道图谱中我们看到碳和硅原子之间属于sp2杂化,同时硅原子周围的电子密度明显要低于碳原子周围的电子密度。对能态密度的计算我们得知碳原子和硅原子分别主导价带和导带。与其它纳米管(BN)有所不同,SiCNT的光学性质更接近于各向同性材料。     

New Energy Spectra Structure of Polaron in Trans-Polyacetylene

In the weakly coupled electron-phonon systems, the existing theory pointed out that the energy spectra of polaron include four electronic bound states. Our work shows that, due to the non-nearest neighbor hopping interactions, the electron-hole symmetry of the energy band structure implied by SSH model is broken, and the numbers of the bound electronic states are changed. For a negative charged polaron, one new bound state is found near the bottom of conduction band, and the original two bound states below the bottom of the valence band and above the top of the conduction band disappear. For a positive charged polaron, five bound states have been found: one of them is an additional bound state at the top of the conduction band, the others are just the states found in the SSH model. Besides, the energy gap 2Δ is slightly shifted by turning on the long-range hopping interactions.     

On the pressure dependence and k-space localization of the deep level states in zinc blend semiconductors doped by the transition metals

An explanation is proposed for the unusual behaviour of the pressure dependent deep level position in Cr-doped InP. It is shown that this level is attached to the subsidiary L-minimum of the conduction band due to the large contribution of the L_1c-point vicinity in the electron density of states, and the symmetry properties of d-impurity states suppressing the hybridization with the band states in the central ?_1c valley of the conduction band.     

Experimental evidence of the hybridization of the electron states of an impurity and the conduction band in the HgSe:Fe system

X-ray absorption spectra from iron donor impurities in mercury selenide have been analyzed in a concentration range where the Fermi energy of conduction electrons is close to the energy of the donor d level. At high impurity concentrations, the resulting spectrum corresponds to the completely filled donor state and coincides with the spectrum of a bivalent iron ion. A transition to an intermediate-filling state is observed with decreasing the concentration. The spectra are quantitatively analyzed in a model implying the existence of a mixture of ions that contain and do not contain a donor electron in a bound state. It has been found that such a model is significantly inconsistent with the experimental data. It has been shown that the concentration dependence of the x-ray spectra corresponds to the manifestation of the significant hybridization of localized and delocalized donor electron states in the conduction band.     

Free electronic states of UO2: Analysis of x-ray absorption by total multiple scattering

The experimentally observed x-ray absorption spectrum of oxygen in UO₂ is analyzed theoretically. The experimental absorption spectrum of oxygen is shown to agree well with details of the density of free p states of oxygen in the conduction band. It is found that a minimum cluster of atoms surrounding an absorbing oxygen ion required to reproduce all the details of the fine structure of the density of states at the bottom of the conduction band is of the order of 40 atoms. An analysis of the densities of the electronic states reveals the existence of hybridization of free p states of oxygen with s states of uranium in the conduction band of UO₂, as well as the exclusion of p states of oxygen by d states of uranium beyond the confines of the energy interval where they are localized. Fiz. Tverd. Tela (St. Petersburg) 41, 1385–1388 (August 1999)     

Variation of the electronic properties of zigzag boron nitride nanotubes by Al-doping: a DFT study

Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes.     

On the electronic structure of Ag chalcogenides

The electronic structure of Ag chalcogenides in the α phase, which exhibit an interesting, electronic semiconducting behaviour as well as the fast ion transport, is discussed on the basis of an energy band structure calculation. As a simplest way of simulating the effect of the Ag ions on the electronic states, some hypothetical crystalline compounds are constructed such as the perovskite, the sodium chloride and the flourite structures. The absolute magnitude of the calculated conduction electron effective mass is quite small irrespectively of the structures, about 10% of the free-electron mass, in semiquantitative agreement with experiments. A deviation from an effective mass approximation near the conduction band bottom is found to be appreciable, and to explain reasonably well experimental results. An origin of these features of the conduction band is a rather strong hybridization of the Ag 5s band and the chalcogen s band. The calculation also shows that the hybridization of the Ag 4d band and the chalcogen p band can affect the absolute magnitude of the hole effective mass appreciably, and that the energy band gap depends sensitively on these s-s and d-p hybridization effects.     

Hybridization effect on phase transitions in the Falicov-Kimball model

The Falicov-Kimball model extended by the hybridization between the localized electron states and the conduction band states is studied in Hartree-Fock approximation. Taking into account the periodicity of the system, the occupation number of the localized levels always varies continuously with the level energy for non-vanishing hybridization. This result is in contradiction with earlier mean-field calculations which are not self- consistent for the periodic model. Since first order phase transitions in intermediate valence compounds such as SmS have been observed experimentally, it follows that their explanation needs a more general theoretical frame than the model considered here.     

单壁碳纳米管中电子的有效质量

解析研究了单壁碳纳米管中电子的有效质量，以及导带底的电子有效质量与其管径和螺旋度的关系.结果表明，单壁碳纳米管的几何结构对其电子有效质量有重要的影响.特别是锯齿形窄隙半导体管，发现其导带底的电子有效质量与管径的平方成反比. 关键词： 单壁碳纳米管 电子有效质量     

Attosecond electron delocalization in the conduction band through the phosphate backbone of genomic DNA

Partial density of states in the empty conduction band of the phosphate backbone sites in DNA was probed using energy-dependent resonant Auger spectroscopy. Results show that genomic DNA with periodic backbones exhibits an extended state despite separation of each phosphate group by an insulating sugar group. In antisense DNA with an aperiodic backbone, the equivalent state is localized. Remarkably rapid electron delocalization occurs at ca. 740 attoseconds for wet DNA, as estimated using the core-hole clock method. Such delocalization is comparable to the Fermi velocity of carbon nanotubes.     

铁电体SrBi2Nb2O2电子能带结构的第一性原理研究

采用第一性原理的方法计算了SrBi₂Nb_2O.9（SBN）的顺电相、铁电相的电子结构.顺电相是间接带隙, 铁电相是直接带隙，它们的大小分别为1.57和2.23 eV.顺电相和铁电相的价带顶均主要来自于O₂p态的贡献.而顺电相和铁电相的导带底则分别来自Nb₄d态和Bi₆p态的贡献.计算表明SBN铁电相的低的漏电流与Bi 6p轨道有关.由顺电相到铁电相时，Nb₄d和O_{2 关键词： 顺电相 铁电相 态密度 电子能带结构}     

Photoelectric spectroscopy of oxide states with MOS structures atT=79 K

AtT=79 K illumination effects with visible and UV light on the drain current were studied forn-channel enhancement-type MOS transistors. The results show that the response of photoelectric measurements is due to electron excitation from oxide states into the silicon surface layer (positive changes of drain current). The oxide states lying near the bottom of the silicon dioxide conduction band are distributed in energy. Oxide states having captured a hole can be discharged by electrons excited from the silicon conduction or valence band (negative changes of drain current) in combination with a tunneling process.     

超快非均质电子转移的优化控制研究(Ⅰ)

本文用三能级的单振动模型,模拟了从二萘嵌苯到TiO2超快电子转移的动力学过程,发现在弱电子转移耦合下,电子在激光场的作用下激发至分子激发态转移然后到半导体导带,在强电子转移耦合下,电子直接由基态转移到半导体导带。在优化控制的理论模拟中以电子激发态的振动基态为目标态,考虑了不同注入位置条件下的电子转移的动力学过程,研究了优化激光场在给定时间内实现目标态的过程,由于从分子激发态到半导体的超快电子转移,只有当分子激发态能级与半导体导带底能级简并时,才能实现较高的目标态产生率。     

Effects of the second and third neighbor hopping interactions on the electronic states of soliton in polyacetylene

We have studied the energy spectra and the electronic states of a soliton in the weakly coupled electron-phonon systems using an extension of SSH model that includes non-nearest neighbor hopping interactions. The results show that: (1) the electron-hole symmetry of the energy band structure implied by SSH model is broken, and the energy gap 2 increases. (2) for a negative charged soliton, only two bound states have been found, one of them is the midgap state, another is a new shallow state near the bottom of the conduction band; for a neutral soliton, all three bound states exist as in the SSH model, but their localizations are strengthened; for a positive charged soliton, four bound states have been found, one of which is an additional state near the top of the conduction band.     

On the anomalous susceptibility of small gap magnetic semiconductors (SmS,SmSe, SmTe)

The magnetic susceptibility of the Sm chalcogenides shows a large dependence on the nature of the anion. In the three compounds (which under pressure become metallic) the energy needed to promote an electron from the 4f shell to the conduction band is very small. We present here a mechanism based on the hybridization between f states and band states that relates the anomalies of the susceptibility with the energy gaps.