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Ab-initio density functional theory study of a WO_3 NH_3-sensing mechanism

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Chinese Physics B 2011年第8期20卷 161-168页

作者：胡明张洁王巍丹秦玉香 School of Electronics and Information Engineering Tianjin University

WO3 bulk and various surfaces are studied by an ab-initio density functional theory technique. The band structures and electronic density states of WO3 bulk are investigated. The surface energies of different WO3 surfaces are compared and then the （002） surface with minimum energy is computed for its NH3 sensing mechanism which explains the results in the experiments. Three adsorption sites are considered. According to the comparisons of the energy and the charge change between before and after adsorption in the optimal adsorption site Olc, the NH3 sensing mechanism is obtained.

关键词： WO3 density functional theory NH3 sensing density of state

A Polymeric Iodiplumbate(Ⅱ) Templated by Conjugated Quaternary Ammonium:Synthesis,Band Structure and Optical Properties

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Chinese Journal of Structural Chemistry 2007年第11期26卷 1315-1321页

作者：成丽川李浩宏陈之荣李俊篯黄长沧蔡增良 College of Chemistry and Chemical Engineering Fuzhou University

A new lead（Ⅱ） iodide coordination polymer [（npq）（PbI3）]n1 （npq = N-propyl- quinolinium） has been synthesized in the presence of npq as structure-directing reagent （SDA）. Compound 1 crystallizes in the orthorhombic system, space group Pbca, with a = 19.158（4）, b = 7.9909（16）, c = 22.929（5） A, V = 3510.2（12） A3, Z = 8, Dc = 2.877 g/cm3, F（000） = 2672, C12H1413NPb, Mr= 760.14, μ（MoKα） = 14.872 mm-1, the final R = 0.0431 and wR = 0.1021 for 3678 observed reflections with Ⅰ 〉 2σ（Ⅰ）. Structure determination indicates that the [PbI3]^-n infinite chains in each unit cell shape the sketch of 1, which could be described as the result of face-sharing distorted PbI6 octahedra running along the b axis. Electrostatic interaction between conjugated organic counter-cations and inorganic moieties presents and contributes to the crystal packing. 1 was further characterized with IR and elemental analysis. Based on the crystal structure data, quantum chemical calculation with DFT method was used to reveal the electronic structure and optical property of 1.

关键词： coordination polymers lead iodide density of state optical property

Predictions of high-pressure structural, electronic and thermodynamic properties of α-Si_3N_4

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Acta Metallurgica Sinica(English Letters) 2012年第2期25卷 131-140页

作者： Benhai YU Dong CHEN Yingbin LI Yonglei JIA College of Physics and Electronic Engineering Xinyang Normal UniversityXinyang 464000China

The plane-wave pseudo-potential method within the framework of first-principles technique is used to investigate the fundamental structural properties of Si3N4. The calculated ground-state parameters agree quite well with the experimental data. Our calculation reveals that α-Si3N4 can retain its stability to at least 45 GPa when compressed below 300 K. No phase transition can be seen in the pressure range of 0-45 GPa and the temperature range of 0-300 K. Actually, the α→β transition occurs at 1600 K and 7.98 GPa. Many thermodynamic properties, such as bulk modulus, heat capacity, thermal expansion, Gr/ineisen parameter and Debye temperature of a-Si3N4 were determined at various temperatures and pressures. Significant differ- ences in these properties were observed at high temperature and high pressure. The calculated results are in good agreement with the available experimental data and previous theoretical values. Therefore, our results may provide useful information for theoretical and experimental investigations of the N-based hard materials like α-Si3N4.

关键词： First-principle Bulk modulus density of state Debye temper ature

Se AND Bi SUBSTITUTION EFFECT IN Sb_2Te_3

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Journal of Wuhan University of Technology(Materials Science) 1998年第3期13卷 21-25页

作者：张建 Wuhan University of Technology China Coll. of Mat. Sci. and Engineering Wuhan University of Technology Wuhan 430070 China

The Discrete Variational Xα Method DV-Xα with an embeded cluster scheme was used to investigate electronic structure, energy levels, charge distribution and chemical bonding in p-type thermoelectric ceramics :Sb2Te3-Bi2Te3-Sb2Se3. The results obtained are in agreement with experiment ones, which are instructive to material design.

关键词： Sb2Te3 solution cluster electronic structure density of state

Orbital Calculations of Kaolinite Surface:on Substitution of Al^(3+) for Si^(4+) in the Tetrahedral Sites

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Journal of Wuhan University of Technology(Materials Science) 2007年第4期22卷 661-666页

作者：洪汉烈 The Faculty of Earth Sciences China University of Geosciences

The surface properties of kaolinite were determined using density functional theory discrete variational method （DFT-DVM） and Gaussian 03 program. A SiO4 tetrahedral hexagonal ring with two A1 octahedra was chosen to model the kaolinite crystal. The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level. Both the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO） of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species, but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface, and thus, shows amphoteric behavior. Substitution of Al3^＋ for Si4＋ in the tetrahedral site linking the vacant Al3^＋ octahedra does not increase the surface chemical reactivity of kaolinite, while substitution of Al3^＋ for Si^4＋ in the tetrahedral site with the apex O linking Al3^＋ octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite, especially acting as electron donors. Additionally, substitution of Al3^＋. for Si^4＋ in the tetrahedral site results in the re-balance of charges, leading to the increase of negative charge of the coordinated O atoms of the AlO4 tetrahedra, and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.

关键词： kaolinite quantum chemistry molecular orbital density of state MOlliken charge

Study of Electronic Structure and Magnetic,Properties of NdFe_(10)M_2 Compounds by LMTO Method

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Journal of Rare Earths 1999年第1期17卷 25-29页

作者：祁守仁张岩向荣黄晓东冯稷 Central China Normal Univ Wuhan China

The electronic structure of NdFe 10 M 2(M=Ti, V, Cr, Mn, Mo, W) compounds were obtained by the linear muffin tin orbit(LMTO) method, and the micro magnetic properties were examined through the total density of state(TDOS) and the local density of state(DOS). The results suggest that there are two mechanisms which compete with each other and are responsible for variations in magnetic moments of NdFe 10 M 2 with intertitial N(or C) atoms, and the volume expansion leads to the enhancement of Fe Fe exchange interaction at 8i and 8f site, with the result that the magnetic moments at both sites increase. Meanwhile, the magnetic moments at 8j site decrease owing to the hybridization between 3d(Fe) and 2p(N or C) orbits.

关键词： Rare earths LMTO method Intertitial atom density of state

Intrinsic Carrier Concentration as a Function of Stress in(001),(101) and(111) BiaxiallyStrained-Si and Strained-Si_(1-x)Ge_x

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Journal of Wuhan University of Technology(Materials Science) 2015年第5期30卷 888-893页

作者：靳钊 QIAO Liping LIU Lidong HE Zhili GUO Chen LIU Ce School of Information Engineering Chang'an University School of Information Engineering Xizang University for Nationalities

Intrinsic carrier concentration(ni) is one of the most important physical parameters for understanding the physics of strained Si and Si1-xGex materials as well as for evaluating the electrical properties of Si-based strained devices. Up to now, the report on quantitative results of intrinsic carrier concentration in strained Si and Si1-xGex materials has been still lacking. In this paper, by analyzing the band structure of strained Si and Si1-xGex materials, both the effective densities of the state near the top of valence band and the bottom of conduction band( Nc and Nv) at 218, 330 and 393 K and the intrinsic carrier concentration related to Ge fraction(x) at 300 K were systematically studied within the framework of KP theory and semiconductor physics. It is found that the intrinsic carrier concentration in strained Si(001) and Si1-xGex(001) and(101) materials at 300 K increases significantly with increasing Ge fraction(x), which provides valuable references to understand the Sibased strained device physics and design.

关键词： strain intrinsic carrier concentration KP theory density of state

Ab initio Study of Electronic Structure and Properties of Crystalline of 1,5-Diamino-1,2,3,4-tetrazole

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Chinese Journal of Chemistry 2011年第2期29卷 217-222页

作者： Shang Jing Zhang Jianguo Zhang Tonglai Shu Yuanjie Zhang Shaowen Huang Huisheng state Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China Institute of Chemical Materials Chinese Academy of Engineering Physics Mianyang Sichuan 621900 China School of Science Beijing Institute of Technology Beijing 100081 China

density functional method was applied to study 1,5-diamino-1,2,3,4-tetrazole （DAT, CH4N6） in both gaseous and bulk states. The banding and electronic structures of crystalline have been investigated at DFT-B3LYP/ 6-311G＊＊ level of theory. Relaxed crystal structure compares well with experimental data. The light fluctuation of the frontier orbital, which is mainly formed by atomic orbital of N（4）（heterocycle）, is the most reactive part of the molecule, which is in good agreement with the experimental results. The energy gap is 9.035 eV, which indicates that DAT is an insulator. The distribution of electrostatic potential is uniform, indicating DAT is insensitive. The charge density of the intermolecular regions in the plane is not overlaid, indicating that the intermolecular interac- tion between the neighboring molecules along this direction in the bulk is very weak. The overlap populations of N（1）--N（2） bonds are much less than those of other bonds, therefore the N（1）--N（2） bonds first rupture by external stimuli.

关键词： 1,5-diamino-l,2,3,4-tetrazole density functional theory band structure density of state charge density

Variable range hopping conduction in n-CdSe samples at very low temperature

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Journal of Semiconductors 2015年第12期36卷 14-17页

作者： M Errai A El Kaaouachi H El Idrissi Physics Department Ibn Zohr University Faculty of Sciences Laboratoire Electronique électrotechnique Automatique et Traitement de l'Information Département Génie ElectriqueFaculté des Sciences et Techniques de Mohammedia Université Hassan Ⅱ Mohammedia Casablanca

We reanalyzed experimental data already published in Friedman J R, Zhang Y, Dai P, et al. Phys Rev B, 1996, 53（15）： 9528. Variable range hopping （VRH） conduction in the insulating three-dimensional n-CdSe samples has been studied over the entire temperature range from 0.03 to 1 K. In the absence of a magnetic field, the low temperature conductivity a of the three samples （A, B and C） obeys the Mott VRH conduction with an appropriate temperature dependence in the prefactor （a = σ0 exp [- （T0/T）]^p with p ≈ 0.25）. This behavior can be explained by a VRH model where the transport occurs by hopping between localized states in the vicinity of the Fermi level, EF, without creation of the Coulomb gap （CG）. On the contrary, no Efros-Shklovskii VRH is observed, suggesting that the density is constant in the vicinity of the EF.

关键词： n-CdSe samples low temperature variable range hopping density of state