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first-principle study on anatase TiO_2 codoped with nitrogen and ytterbium

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Journal of Semiconductors 2010年第3期31卷 1-6页

作者：高攀张学军周文芳吴晶柳清菊 Yunnan Key Laboratory of Nanomaterials & Technology Yunnan University Department of Physics and Electric Information Engineering Hunan City University

Crystal structures, electronic structures and optical properties of nitrogen and ytterbium doping anatase TiO2 were calculated by first principles with the plane-wave ultrasoft psendopotential method based on the density functional theory. The calculated results show that the octahedral dipole moments in TiO2 increase due to the changes in lattice parameters, bond length and charges on atoms, which is very effective for the separation ofphotoexcited electron-hole pairs and the improvement of the photocatalytic activity ofTiO2. The interband transition between OPπ states and Yb4f states make nitrogen and ytterbium doped TiO2 manifest greater absorption coefficients in the visible-light region.

关键词： YiO2 N＋Yb-doped first-principle

MOLECULAR DYNAMICS SIMULATION OF INTERFACIAL DEFECTS WITH MODIFIED POTENTIAL BASED ON THE first-principle

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Acta Mechanica Solida Sinica 2010年第5期23卷 400-406页

作者： Dongwei Ren Jinquan Xu 1(School of Naval Architecture and Civil Engineering,Shanghai Jiaotong University,Shanghai 200240,China) School of Naval Architecture and Civil Engineering Shanghai Jiaotong University Shanghai China

The interfacial molecular structure of materials with different lattice constants is simulated by using the method of molecular dynamics （MD）. Potential of modified analytical embedded atom method （MAEAM） is used for nominterfacial atoms. To simulate the state of interracial atoms, further modifications are applied to the MAEAM potential based on the first- principle simulation results. It is concluded that a small change of potential may greatly influence the interfacial molecular structure. Void and diffusions can be observed in the simulation results. It is also found that the pre-existed dot defects before bonding can decrease the number of interfacial defects greatly, thereby, can increase the strength of the interface.

关键词： molecular dynamics interface defect potential first-principle

first-principle Calculations of Hardness and Melting Point of Mo_2C

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Journal of Materials Science & Technology 2009年第3期25卷 419-422页

作者： X.R. Wang M.F. Yan H.T. Chen School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

This paper has constructed two kinds of atomic and electronic models for hexagonal β-Mo2C and orthorhombic α-Mo2C. The optimized lattice parameters, elastic constant matrixes and overlap population for Mo2C crystal cells have been obtained to realize the characterization of the hardness and melting point of the two structures by the first-principles plane wave pseudo potential method based on the density functional theory. The results reveal that the calculated lattice parameters of the Mo2C crystal cells agree with the experimental and other calculated data. The calculated melting point/hardness are 2715 K/11.38 GPa for β-Mo2C and 2699 K/10.57-12.67 GPa for α-Mo2C, respectively. The calculated results from the density of states （DOS） demonstrate that the hybridization effect between Mo-3d and C-2p states in α-Mo2C crystal cell is much stronger than that in β-Mo2C one.

关键词： first-principle Mo2C Hardness Melting point Density of states

first-principle studies of radioactive fission productions Cs/Sr/Ag/I adsorption on chrome-molybdenum steel in Chinese 200 MW HTR-PM

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Nuclear Science and Techniques 2017年第6期28卷 123-132页

作者： Chuan Li Chao Fang Chen Yang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua University

Chrome-molybdenum steel(2·1/4Cr1Mo) is one of the main products of steam generation.The adsorption behaviors of radioactive fission products on2·1/4Cr1Mo surface are critical in the analysis of HTR-PM.Here,the adsorption behavior of cesium,strontium,silver and iodine on 2·1/4Cr1Mo was investigated with first-principle calculations that the Ag and I atoms prefer to be adsorbed at the square hollow site of the face-centered cubic iron cell with a binding energy of about 1 and 3 eV,respectively.In contrast,Cs and Sr atoms are not adsorbed on the surface of the 2·1/4Cr1Mo.These results are again confirmed via analysis of charge density differences and the densities of state.Furthermore,the adsorption rates of these fission products show that only I and Ag have significant adsorption on the metal substrate.These adsorption results explain the amount of adsorbed radionuclides for an evaluation of nuclear safety in HTR-PM.These micro-pictures of the interaction between fission products and materials are a new and useful way to analyze the source term.

关键词： first-principle calculation Fission product Adsorption behavior HTR-PM

A first-principle investigation of the oxygen defects in Si_3N_4-based charge trapping memories

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Journal of Semiconductors 2014年第1期35卷 40-45页

作者：罗京卢金龙赵宏鹏代月花刘琦杨金蒋先伟许会芳 School of Electronics and Information Engineering Anhui University Laboratory of Nano-Fabrication and Novel Device Integrated Technology Institute of Microelectronics Chinese Academy of Sciences

Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride （β-Si3N4） has been carried out. firstly, it is found that substitutional oxygen is most likely to form clusters at three sites in Si3N4 due to the intense attractive interaction between oxygen defects. Then, by using three analytical tools （trap energy, modified Bader analysis and charge density difference）, we discuss the trap abilities of the three clusters. The result shows that each kind of cluster at the three specific sites presents very different abilities to trap charge carriers （electrons or holes）： two of the three clusters can trap both kinds of charge carriers, confirming their amphoteric property; While the last remaining one is only able to trap hole carriers. Moreover, our studies reveal that the three clusters differ from each other in terms of endurance during the program/erase progress. Taking full account of capturing properties for the three oxygen clusters, including trap ability and endurance, we deem holes rather than electrons to be optimal to act as operational charge carriers for the oxygen defects in Si3N4-based charge trapping memories.

关键词： charge trapping memory silicon nitride substitutional oxygen capturing property first-principle

Approach to Inversion Design of Dielectric Material Based on the first-principle

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Chinese Journal of Electronics 2017年第1期26卷 50-57页

作者： MIAO Qiang WU Dewei HE Jing YANG Chunyan XIE Lei Information and Navigation College of Air Force Engineering University Ming De College of Northwestern Polytechnical University

The first-principle is an effective method for the material property calculation. One inversion design idea of dielectric material based on the first-principle was put forward. In this kind of material design thought,the specific demanded dielectric property of material is the starting point of the whole design course. The atomic structure characteristic of the material is solved using the inversion model based on the first-principle. And the key issues needing researching were discussed, these problems were quantized structure of electromagnetic and optic field,the quantized polarization theory of dielectric material, the uniform calculation method of dielectric property and the dielectric material inversion model.

关键词： first-principle Dielectric material Dielectric property Inversion design

first-principle Calculations of V/Fe Doped Anatase TiO_2

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Chinese Journal of Aeronautics 2006年第B12期19卷 162-166页

作者： CAO Hong-hong CHEN Qiang WANG Tian-min School of Science Beijing University of Aeronautics and Astronautics Beijing 100083 China

The electronic structures of the titanium dioxide（TiO2） doped with V and Fe were analyzed by using first-principle calculations based on the density functional theory（DFT） with the full potential linearized augmented plane wave method （FP-LAPW）. The fully optimized structure and the relaxation introduced by impurity were obtained by minimizing the total energy and atomic forces. The unit cell of the V-doped anatase TiO2 is smaller than that of the non-doped one, but for the Fe-doped one, the case is just the opposite. It is found that the apical Ti-O and impurity-O bond lengths of the V/Fe-doped anatase TiO2 are greater than those of the non-doped structure, but smaller for the equatorial bond length. Through the band structures and the density of states, the V-doped TiO2 is shown to be a kind of half-metal, while the Fe-doped TiO2 a kind of metal. The magnetic moments of the V/Fe-doped system are mainly generated by the dopants. The results may be helpful for us to understand the experimental outcome of this system.

关键词： first-principle FP-LAPW DMS anatase electronic properties

first-principle study on phase Al_(0.8)Ni_3Sn_(0.2) in Sn-Ni-Al alloy as anode for lithium ion battery

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Chinese Physics B 2010年第11期19卷 521-527页

作者：黄钊文胡社军侯贤华赵灵智汝强李伟善张志文 School of Physics and Telecommunication Engineering South China Normal University Key Laboratory of Electrochemical Technology on Energy Storage and Power Generation of Guangdong Higher Education Institutes South China Normal University

The mechanism of lithium intercalation/deintercalation for phase Al0.8Ni3Sn0.2 as anode material used in lithium ion battery was studied carefully based on the first-principle plane wave pseudo-potential method. The calculated results indicated that SnNi Al alloy had high theoretical capacity when used as anode material, however, there was high initial irreversible capacity loss because of the large volume expansion. Therefore the technological parameters during preparing the Sn-Ni-Al anode should be controlled strictly to make the content of Al0.8Ni3Sn0.2 phase as low as possible and to make the anode consist of promising Sn-Ni and AI-Ni phases. For comparison, an experiment based on magnetron sputtering was done. The result showed that the calculation is in good agreement with the experiment. We found that the first-principle investigation method is of far-reaching significance in synthesising new commercial anode materials with high capacity and good cycle performance.

关键词： Sn-Ni-Al alloy first-principle lithium ion battery

Magnetism induced by nonmagnetic dopants in zinc-blende SiC: first-principle calculations

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Science China(Physics,Mechanics & Astronomy) 2010年第1期53卷 1-10页

作者： LIU ZhaoQing & NI Jun Department of Physics and Key Laboratory of Atomic and Molecular Nanoscience (Ministry of Education), Tsinghua University, Beijing 100084, China Department of Physics and Key Laboratory of Atomic and Molecular Nanoscience (Ministry of Education) Tsinghua University Beijing China

Magnetism induced by the nonmagnetic dopants in the zinc-blende SiC (3C-SiC) is investigated by first-principle calculations. The atoms of the first 20 elements in the periodic table except inert gas are used to replace either Si or C atoms as dopants. We find that some nonmagnetic substitutional dopants (mainly the Group IA, Group IIA, Group IIIB, and Group VIIB elements) prefer the spin-polarized ground states with local magnetic moments. In general, the condition for obtaining the local magnetic moments and the magnetic ground state requires that the dopants are p-type and have large electronegativity difference from the neighboring host atoms. The magnetic moments can be tuned over a range between 1 μ B and 3 μ B by doping with the nonmagnetic elements. The nearest-neighbor exchange couplings J 0 between the local magnetic moments are quite large and the codoping method is proposed to increase the dopant concentration. These imply that the nonmagnetic doping in SiC may exhibit collective magnetism. Moreover, the Group IIA Mg and Ca atoms substituting the preferred Si atoms favor the ferromagnetic ground states with the half-metallic electronic properties, which suggests that Mg or Ca substitutional doping on the Si sites in SiC could be a potential route to fabricating the diluted magnetic semiconductors.

关键词： nonmagnetic dopant magnetism SiC diluted magnetic semiconductor first-principle calculation