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density-functional theory investigation of electronic structure,elastic properties,optical properties,and lattice dynamics of Ba_2Zn WO_6

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Chinese Physics B 2013年第6期22卷 507-511页

作者：郭三栋 Department of Physics School of SciencesChina University of Mining and Technology

The electronic structures, optical dielectric functions, elastic properties, and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation. The density of states and distributions of charge density show that O and Ba tend toward ionic bond, but O and W or Zn display the covalent bond character. The calculated energy band structure shows that Ba2ZnWO6 is a wide indirect band gap semiconductor. The static value 2.28 of the refractive index is attained. The analysis of the elastic properties of Ba2ZnWO6 indicates a rather weak elastic anisotropy. The phonon dispersion is calculated, suggesting no structural instability, which is agreement with the recent low temperature neutron diffraction experiments. The mensurability Cv （phonon heat capacity） as the function of the temperature is also calculated to judge our results for future experiment.

关键词： semiconductor double perovskite structure density-functional theory

A density-functional theory for (BAs) n clusters (n=1-14):structures,stabilities and electronic properties

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Chinese Physics B 2011年第2期20卷 201-208页

作者：刘志锋雷雪玲刘立仁刘火雁祝恒江 School of Physics and Electronic Engineering Xinjiang Normal University

This paper investigates the lowest-energy structures, stabilities and electronic properties of （BAs）n clusters （n=1- 14） by means of the density-functional theory. The results show that the lowest-energy structures undergo a structural change from two-dimensional to three-dimensional when n ： 4. With the increase of the cluster size （n=6）, the （BAs）n clusters tend to adopt cage-like structures, which can be considered as being built from B2As2 and six-membered rings with B-As bond alternative arrangement. The binding energy per atom, second-order energy differences, vertical electron affinity and vertical ionization potential are calculated and discussed. The caculated HOMO-LUMO gaps reveal that the clusters have typical semiconductor characteristics. The analysis of partial density of states suggests that there are strong covalence and molecular characteristics in the clusters.

关键词： (BAs)n clusters density-functional theory lowest-energy structures electronic proper-ties

Initial Oxidation of γ-TiAl(111) Surface:density-functional theory Study

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Journal of Materials Science & Technology 2009年第4期25卷 569-576页

作者： Hong Li Shaoqing Wang Hengqiang Ye Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Graduate School of Chinese Academy of Sciences Beijing 100039 China Electron Microscope Lab Peking University Beijing 100871 China

In this paper, we reported a first-principles investigation on the structural and electronic properties of O adsorption on the γ-TiAI（111） surface, to illustrate the oxidation process. It has been found that：（1） rather than stopping with one full monolayer of coverage, oxygen adsorption continues till two monolayer coverage, rendering an oxide-like structure; （2） full structural relaxation makes the surface oxide layer denser and more stable, which hinders the subsequent O adsorption （oxidation） process. In addition, the transformation from metal to oxide surface was identified by analyzing the local density of states through the oxidation steps, which was in good agreement with experimental results.

关键词： density-functional theory γ-TiAl Surface Oxidation

Application of density-functional theory to studying methylation with dimethyl carbonate and dimethyl sulfate

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Journal of Chongqing University 2007年第3期6卷 161-165页

作者：张定林 Department of Chemistry Third Military Medical University

The activities of dimethyl carbonate and dimethyl sulfate as a methylation reagent were studied by density- functional theory （DFT）. B3LYP/6-31G（d, p） methods were used to optimize the structures of dirnethyl carbonate and dimethyl sulfate and calculate theirs charge densities. Dimethyl sulfate is easier than dimethyl carbonate to react with a nucleophUic reagent. In dimethyl sulfate, the alkoxy carbons are the only reactive atomic nucleus because of steric hindrance. A nucleophilic reagent is more likely to react with carbonyl carbons than alkoxy carbons of dimethyl carbonate; in the presence of a Lewis acid, the phenyl nucleophilic reagent reacts with the Lewis acid first. Lewis acid increases the negative charge density of a nucleophUic reagent in polar solvent, and also incurs an accretion of steric hindrance. Polar solvent avails to ionize dimethyl carbonate and thus enables the reaction of methylation. The frequencies of transition state calculated by Gaussion 03 confirm the inferred reaction mechanism. The harvest rates of 4-methoxyphenol in the experiments of methylation reactions of hydroquinone with respectively dimethyl carbonate and dimethyl sulfate support the foregoing theortical conclusions.

关键词： density-functional theory dimethyl carbonate dimethyl sulfate

F-μbond length andμSR depolarization spectrum calculation for fluoride using two-component density functional theory

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Chinese Physics B 2023年第8期32卷 120-123页

作者：潘智康邓力潘子文原钺张宏俊叶邦角 State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China

First-principles calculation of muons in ionic fluorides has been proposed ***,there is a considerable difference between the obtained F-μbond length and the experimental data obtained by muon spin relaxation(μSR).Considering that the difference may be caused by ignoring the quantum effect of muons,we use two-component density functional theory(TCDFT)to consider the quantized muon and recalculate the bond length and theμSR depolarization *** testing several muon-electron correlation,we show that TCDFT can give better results than the commonly used“DFT+μ”.

关键词： muon spin relaxation/rotation fluoride density-functional theory

Electronic structures of impurities and point defects in semiconductors

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Chinese Physics B 2018年第11期27卷 358-371页

作者： Yong Zhang Department of Electrical and Computer Engineering University of North Carolina at Charlotte Charlotte NC 28223 US

A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for ＂shallow＂ and ＂deep＂impurities and point defects. The underlying physics of computational results using different density-functional theorybased approaches are discussed and interpreted in the framework of the bound exciton model.

关键词： semiconductor shallow impurity deep impurity bound exciton density-functional theory effective-mass theory hydrogen model

Conformational change-modulated spin transport at single-molecule level in carbon systems

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Chinese Physics B 2022年第12期31卷 460-468页

作者： Yandong Guo Xue Zhao Hongru Zhao Li Yang Liyan Lin Yue Jiang Dan Ma Yuting Chen Xiaohong Yan College of Electronic and Optical Engineering Nanjing University of Posts and TelecommunicationsNanjing 210046China College of Natural Science Nanjing University of Posts and TelecommunicationsNanjing 210046China Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province Nanjing 210023China College of Science Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in *** by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain *** is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized ***,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin *** analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin *** a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application *** findings may throw light on the development of spintronic devices.

关键词： spin-dependent electronic transport molecular device dual-spin filter density-functional theory

Anharmonic multi-phonon nonradiative transition: A n ab initio calculation approach

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Science China(Physics,Mechanics & Astronomy) 2020年第7期63卷 97-103页

作者： Yao Xiao ZiWu Wang Lin Shi XiangWei Jiang ShuShen Li LinWang Wang State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology Department of PhysicsSchool of ScienceTianjin UniversityTianjin 300354China Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of SciencesSuzhou 215123China Materials Science Division Lawrence Berkeley National LaboratoryBerkeley 94720USA

Nonradiative carrier recombinations at deep centers in semiconductors are of great importance for both fundamental physics and device *** this article,we provide a revised analysis of Huang's original nonradiative multi-phonon(NMP)theory with ab initio ***,we confirmed at the first-principles level that Huang's concise formula gives the same results as the matrix-based formula,and that Huang's high-temperature formula provides an analytical expression for the coupling constant in Marcus ***,we correct for anharmonic effects by taking into account local phonon-mode variations for different charge states of a *** corrected capture rates for defects in GaN and SiC agree well with experiments.

关键词： multi-phonon transition nonradiative point defect anharmonic density-functional theory

Design of p-n homojunctions in metal-free carbon nitride photocatalyst for overall water splitting

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Chinese Journal of Catalysis 2021年第3期42卷 501-509页

作者： Gang Zhao Shuhua Hao Jinghua Guo Yupeng Xing Lei Zhang Xijin Xu Laboratory of functional Micro-nano Material and Device School of Physics and TechnologyUniversity of JinanJinan 250022ShandongChina State Key Lab of Crystal Materials Shandong UniversityJinan 250100ShandongChina

Two-dimensional(2D)carbon nitride(CN)photocatalysts are attracting extensive attention owing to their excellent photocatalytic *** this study,we successfully prepared CN materials with heterogeneous structures via hydrothermal treatment,high-temperature roasting,ball milling,sintering,and other *** from interface interactions in hybrid architectures,the CN photocatalysts exhibited high photocatalytic *** rate of hydrogen production using these CN photocatalysts reached 17028.82μmol h^(−1)g^(−1),and the apparent quantum efficiency was 11.2%at 420 *** ns-level time-resolved photoluminescence(PL)spectra provided information about the time-averaged lifetime of fluorescence charge carriers;the lifetime of the charge carriers causing the fluorescence of CN reached 9.99 ***,the CN photocatalysts displayed satisfactory results in overall water splitting without the addition of sacrificial *** average hydrogen and oxygen production rates were 270.95μmol h^(−1)g^(−1)and 115.21μmol h^(−1)g^(−1)in 7 h,respectively,which were promising results for the applications of the catalysts in overall water splitting *** investigated the high efficiency of the prepared CN photocatalysts via a series of tests(UV-vis diffuse reflectance spectroscopy,photocurrent response measurements,PL emission spectroscopy,time-resolved PL spectroscopy,and Brunauer-Emmett-Teller analysis).Furthermore,the Mott-Schottky plot and current-voltage curve were acquired via electrochemical *** fabricated CN photocatalyst had a small p-n junction in its heterogeneous structure,which further enhanced its photocatalytic ***,this work can promote the development of CN photocatalysts.

关键词： 2D Metal-free photocatalyst Carbon nitride Overall water splitting Time-resolved photoluminescence spectra density-functional theory Heterogeneous structure