Electronic structure of semiconducting nanotubes adsorbed on metal surfaces

A total-energy electronic-structure calculation is performed to explore energetics and electronic structures of nanotubes adsorbed on metal surfaces. We find that the charge transfer from metal surfaces to the nanotubes takes place depending on both the electronic structures of the adsorbed nanotubes and the work functions of the metal surfaces. In addition, we also find a substantial hybridization between the electron states of metal atoms and those of the nanotubes, which results in the metal-induced inhomogeneous charge distribution in the nanotubes.     

高压下ZnS的电子结构和性质

运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法，计算研究了闪锌矿结构的ZnS晶体在不同的外界压强下的电子结构. 通过分析发现，随着外界压强的增大，晶格常数和键长在不断缩小，从S原子向Zn原子转移的电荷越来越少，Zn—S键的共价性逐渐增强，Zn原子和S原子的态密度都有不同程度的变化，而且还有向低能量移动的趋势. 当外界压强达到24GPA时，ZnS从直接带隙半导体变成间接带隙半导体，而且随着压强的增大，间接带隙逐渐变小，直接带隙逐渐增大. 关键词： 闪锌矿结构 态密度 能带结构 密度泛函理论     

高压下ZnSe的电子结构和光学性质

运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法,利用第一性原理计算了不同的压强下ZnSe晶体闪锌矿结构,得到了它的平衡晶格常数、总能量、电子态密度分布、能带结构、光反射与吸收系数等性质,详细讨论了高压下ZnSe的电子结构,并且结合实验结果定性地分析了高压下的光学性质. 关键词： 闪锌矿结构 态密度 能带结构 密度泛函理论     

高压下AlN的电子结构和光学性质

运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法,利用第一性原理计算了不同压强下六方纤锌矿结构AlN晶体的晶格常数、总能量、电子态密度、能带结构、光反射系数与吸收系数。通过比较能带结构的变化行为,得出 AlN在16.7Gpa附近存在等结构相变,即由直接带隙结构转变为间接带隙结构。同时,结合高压下的态密度分布图和能级移动情况,分析了AlN在高压下的光学性质,吸收谱有向高能端移动(蓝移) 的趋势。     

Electronic structure and thermodynamic properties of LiBC under high pressure

This paper investigates the electronic structure and thermodynamic properties of LiBC in the hexagonal structure by using the generalized gradient approximation （GGA） and local density approximation correction scheme in the frame of density functional theory. The geometric structure of LiBC under zero pressure, and the dependences of the normalized lattice parameters a/ao and c/co, the ratio e/a, the normalized primitive volume V/Vo on pressure are given. The thermodynamic quantity （including the heat capacity Cv, Debye temperature 6~D, thermal expansion a and Grfineisen parameter -y） dependences on temperature and pressure are obtained through the GGA method and the quasi-harmonic Debye model. The band structures and density of state of LiBC under different pressures have also been analysed.     

Electronic level diagram and structure of metastable centers in CdF2:Ga and CdF2:In semiconducting crystals

A study is reported of the optical properties of wide-gap, predominantly ionic cadmium fluoride crystals in photo-and thermally stimulated transformations of metastable indium and gallium centers. An analysis of these properties leads one to a conclusion of gallium having two metastable states (two types of deep centers). The deep-center binding energies and the barriers separating the shallow (hydrogenic) and deep centers have been determined for both impurities. Configuration-coordinate diagrams are developed, and microscopic models for the deep centers are proposed. It is concluded that these centers are identical with the metastable DX centers in typical semiconducting crystals. Thus cadmium fluoride is the most ionic among the crystals where DX centers have thus far been found. The potential of using such crystals for optical information recording is discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 2130–2136 (December 1997)     

高压下AlN的电子结构和光学性质

运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法,利用第一性原理计算了不同压强下六方纤锌矿结构AlN晶体的晶格常数、总能量、电子态密度、能带结构、光反射系数与吸收系数。通过比较能带结构的变化行为,得出 AlN在16.7Gpa附近存在等结构相变,即由直接带隙结构转变为间接带隙结构。同时,结合高压下的态密度分布图和能级移动情况,分析了AlN在高压下的光学性质,吸收谱有向高能端移动(蓝移) 的趋势。     

Electronic structure of CsCdCl3 single crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 6, pp. 988–991, December, 1990.     

Electronic structure and optical property of boron doped semiconducting graphene nanoribbons

We present a system study on the electronic structure and optical property of boron doped semiconducting graphene nanoribbons using the density functional theory. Energy band structure, density of states, deformation density, Mulliken popular and optical spectra are considered to show the special electronic structure of boron doped semiconducting graphene nanoribbons. The C—B bond form is discussed in detail. From our analysis it is concluded that the Fermi energy of boron doped semiconducting graphene nano...     

Electronic structure and physical properties of bcc selenium under high pressure

Abstract

Here we report a theoretical calculation of the band structure and superconductivity of Se in the bcc phase. The energy band structure and the effect of pressure on the band structure is obtained by means of the Linear Muffin-Tin Orbital method within the atomic sphere approximation. The superconducting transition temperature (T_c) is calculated using McMillan's formula and we predict the value of T_c at 115.3 Gpa as 2.3 K. Further increase in presssure decreases the T_c values. The normal state electrical resistivity at 115.3 Gpa is 1.43 fl cm, with further increase in pressure the resistivity decreases, which is a typical behaviour of number of elemental metals under pressure.     

Electronic structure and lattice properties of zinc-blende InN under high pressure

Dependencies of electronic structure and lattice properties of InN with zinc-blende structure on hydrostatic pressure are presented based on band structures computed using the empirical pseudopotential method. The pressure behavior of the pseudopotential form factors have been analyzed. The effect of pressure on the density of states has been examined. Trends in bonding and ionicity under pressure are also discussed. Our results show as well that the absolute value of the Fourier transform of the valence charge density might be useful in the prediction of the phase transition in zinc-blende materials. Received 25 May 2001 and Received in final form 16 January 2002     

Electronic structure and optical spectra of oxyanion crystals

Band structure of lithium, sodium, and potassium nitrites, nitrates, chlorates, perchlorates, sulfites, and sulfates together with the state density and the imaginary part of the complex dielectric permittivity is calculated by the DFT-LDA method with the Perdew and Zunger (PZ) correlation potential using the software package CRYSTAL06 on the uniform grid comprising 512 points of the Brillouin zone in the approximation of the direct interband transitions and constant matrix element. Good agreement of experimental and theoretical optical spectra is established. It is demonstrated that the main specific features of the optical spectra at energies of 5–12 eV are determined by the complex anion structure and depend only slightly on the cation structure. The cation excitation energies are 25‒28 eV for sodium salts and 15‒18 eV for potassium ones.     

Tunable photonic crystals with semiconducting constituents

We propose that the photonic band structure (PBS) of semiconductor-based photonic crystals (PCs) can be made tunable if the free-carrier density is sufficiently high. In this case, the dielectric constant of the semiconductor, modeled as varepsilon(omega) = varepsilon(0)(1-omega(2)(p)/omega(2)), depends on the temperature T and on the impurity concentration N through the plasma frequency omega(p). Then the PBS is strongly T and N dependent; it is even possible to obliterate a photonic band gap. This is shown by calculating the 2D PBS for PCs that incorporate either intrinsic InSb or extrinsic Ge.     

Submillimetre spectra of crystals under high pressure

Submillimetre spectra have been recorded from various crystalline solids, mostly alkali halides, which were being subjected to high gas pressure. The apparatus could be used at pressures up to IGPa at any temperature in the range 77–400K, but most of the results so far have been recorded at either 77 or 300K. The main emphasis will be on our efforts to measure the frequency shifts with sufficient accuracy to obtain information about the temperature and pressure dependence of the mode Gruneisen parameters.     

γ-Si3N4在高压下的电子结构和物理性质研究

采用基于密度泛函平面波赝势方法(PWP)和广义梯度近似(GGA-PW91),计算了不同压强下γ-Si3N4的电子结构、光学性质和力学性质.基于计算结果,分析讨论了γ-Si3N4各物理参数随外压力的变化规律.计算表明,γ-Si3N4是一种适合于在高压条件下工作的材料.     

高场强下半导体沿面闪络现象的研究进展

综述了国内外半导体沿面闪络的研究现状,阐述了电极结构的类型和影响闪络的主要因素;根据自定义的等值电导参数将闪络的发展划分为欧姆电导、局部闪络和贯通闪络3个阶段;通过对表面细丝电流的热过程进行实验和仿真研究,认为表面细丝电流通道的温度可以接近材料熔点,这一结果同时也支持了表面发热导致气体分子解吸附的假设;进一步通过气体解吸附的实验初步确定了存在外部的闪络通道。     

高场强下半导体沿面闪络现象的研究进展

 综述了国内外半导体沿面闪络的研究现状,阐述了电极结构的类型和影响闪络的主要因素;根据自定义的等值电导参数将闪络的发展划分为欧姆电导、局部闪络和贯通闪络3个阶段;通过对表面细丝电流的热过程进行实验和仿真研究,认为表面细丝电流通道的温度可以接近材料熔点,这一结果同时也支持了表面发热导致气体分子解吸附的假设;进一步通过气体解吸附的实验初步确定了存在外部的闪络通道。     

Proton channeling in ionic and semiconducting single crystals

Measurements have been made of the energy distributions of protons passing through NaCl, KCl, Si, and Ge single crystals at various angles with respect to the {100} and {110} planes. The fraction of protons passing through lattice channels has been evaluated, and its dependences on the angle of incidence, the chemical composition of the sample, and the proton energy have been found.     

Electronic structure of transition metals under pressure

Conclusions In this short review we have tried to demonstrate the advances made in the intensive study of the behavior of the electronic structure of metals under pressure in recent years. The alloys of transition metals, including intermetallic ordered compounds, have for the time being proved to lie outside the scope of this review, mainly because of the lack, in practice, of theoretical calculations in this area. Clearly, progress in this field is also being held up by the lack of detailed experimental investigations devoted to the behavior of alloys under pressure. This is due to the complexities involved in carrying out many traditional experimental procedures under high pressures. We should like to emphasize, however, that at the present time theoretical calculations have taken on a predictive power and this gives reason to hope that progress in calculations will in turn stimulate progress in experimentation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 50–62, December, 1982.