检索结果-南通市图书馆

Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN_2 and PtN_2

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2009年第9期18卷 3934-3939页

作者：赵文杰王渊旭 Institute for Computational Materials Science and Physics Department Henan University

This paper studies the elastic and electronic structure properties of two new low-energy structures of PdN2 and PtN2 by first-principles calculations. It finds that tetragonal and monoclinic structures are more stable than a pyrite one. The always positive eigenvalues of the elastic constant matrix confirm that both the tetragonal and monoclinic structures are elastically stable. The origin of the low bulk modulus of the two structures is discussed. The results of the calculated density of states show that both of the two low-energy structures are metallic.

关键词： palladium nitride elastic constant structure electronic structure

Ab initio study of the electronic structure and elastic properties of Al_5C_3N

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2011年第12期20卷 309-314页

作者：徐学文胡龙宇霄卢遵铭范英李养贤唐成春 School of Materials Science and Engineering Hebei University of Technology

We investigate the electronic structure, chemical bonding and elastic properties of the hexagonal aluminum carbonitride, Al5C3N, by ab initio calculations. Al5C3N is a semiconductor with a narrow indirect gap of 0.81 eV. The valence bands below the Fermi level （EF） originate from the hybridized Al p-C p and A1 p-N p states. The calculated bulk and Young＇s moduli are 201 GPa and 292 GPa, which are slightly lower than those of Ti3SiC2. The values of the bulk-to-shear-modulus and bulk-modulus-to-c44 are 1.73 and 1.97, respectively, which are higher than those of Ti2AlC and Ti2AlN, indicating that Al5C3N is a ductile ceramic.

关键词： electronic structure chemical bonding elastic properties ductility

Effect of the stoichiometry on the electronic structure of the Ni(111)/α-Al_2O_3(0001) interface:a first-principles investigation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2008年第7期17卷 2655-2661页

作者：施思齐田中真悟香山正憲 Department of Physics Center for Optoelectronics Materials and DevicesZhejiang Sci-Tech UniversityXiasha College Park Materials Science Research Group Research Institute for Ubiquitous Energy DevicesNational Institute of Advanced Industrial Science and Technology

In this paper first-principles calculations of Ni（111）/α-Al2O3（0001） interfaces have been performed, and are compared with the preceding results of the Cu （111）/α-Al2O3（0001） interface [2004 Phil. Mag. Left. 84 425]. The AI- terminated and O-terminated interfaces have quite different adhesion mechanisms, which are similar to the Cu（111）/α Al2O3（0001） interface. For the O-terminated interface, the adhesion is caused by the strong O-2p/Ni-3d orbital hybridization and ionic interactions. On the other hand, the adhesion nature of the Al-terminated interface is the image-like electrostatic and Ni-Al hybridization interactions, the latter is substantial and cannot be neglected. Charge transfer occurs from Al2O3 to Ni, which is opposite to that in the O=terminated interface. The charge transfer direction for the Al-terminated and O-terminated Ni（111）/α-A1203（0001） interfaces is similar to that in the corresponding Cu（111）/α- Al2O3（0001） interface, but there exist the larger charge transfer quantity and consequent stronger adhesion nature, respectively.

关键词： metal/ceramic interface stoichiometry electronic structure first-principles calculations

Effects of oxygen vacancy location on the electronic structure and spin density of Co-doped rutile TiO_2 dilute magnetic semiconductors

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第4期21卷 524-531页

作者：孙运斌张向群李国科成昭华 State Key Laboratory of Magnetism Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing 100190China

According to density functional theory （DFT） using the plane wave base and pseudo-potential, we investigate the effects of the specific location of oxygen vacancy （Vo） in a （Ti,Co）06 distorted octahedron on the spin density and magnetic properties of Co-doped rutile Ti02 dilute magnetic semiconductors. Our calculations suggest that the Vo location has a significant influence on the magnetic moment of individual Co cations. In the case where two Co atoms are separated far away from each other, when the Vo is located at the equatorial site of a Co-contained octahedron, the ground state of the two Co cations is d6（t3g↑, t23g ↓） without any magnetic moment. However, if the Vo is located at the apical site, these two Co sites have different ground states and magnetic moments. The spin densities are also observed to be modified by the exchange coupling between the Co cations and the location of Vo. Some positive spin polarization is induced around the adjacent O ions.

关键词： oxygen vacancy impurity distribution electronic structure

First-principles study of La and Sb-doping effects on electronic structure and optical properties of SrTiO_3

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2010年第1期19卷 433-440页

作者：贠江妮张志勇闫军锋邓周虎 School of Information Science and Technology Northwest University Institute of Photonics and Photon-Technology of Northwest University

The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of SrTiO3, and its structural stability can be improved by La doping. The La^3＋ ion fnlly acts as an electron donor in Sr0.875La0.125TiO3 and the Fermi level shifts into the conduction bands （CBs） after La doping. As for SrSb0.125Ti0.87503, there is a distortion near the bottom of the CBs for SrSb0.125Ti0.87503 after Sb doping and an incipient localization of some of the doped electrons trapped in the Ti site, making it impossible to describe the evolution of the density of states （DOS） within the rigid band model. At the same time, the DOSs of the two electron-doped systems shift towards low energies and the optical band gaps are broadened by about 0.4 and 0.6 eV for Sr0.875La0.125TiO3 and SrSb0.125Ti0.87503, respectively. Moreover, the transmittance of SrSb0.125Ti0.87503 is as high as 95% in most of the visible region, which is higher than that of Sr0.875La0.125TiO3（85%）. The wide band gap, the small transition probability and the weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the significant optical transparency of SrSb0.125Ti0.875O3.

关键词： density functional theory SrTiO3 doping electronic structure

First-principles calculation of electronic structure of Mg_xZn_(1-x)O codoped with aluminium and nitrogen

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2011年第1期20卷 528-533页

作者：张明张川晖申江 Institute of Applied Physics University of Science and Technology Beijing

Aiming at developing p-type semiconductors and modulating the band gap for photoelectronic devices and band engineering, we present the ab initio numerical simulation of the effect of codoping ZnO with Al, N and Mg on the crystal lattice and electronic structure. The simulations are based on the Perdew-Burke-Ernzerhof generalised-gradient approximation in density functional theory. Results indicate that electrons close to the Fermi level transfer effectively when Al, Mg, and N replace Zn and O atoms, and the theoretical results were consistent with the experiments. The addition of Mg leads to the variation of crystal lattice, expanse of energy band, and change of band gap. These unusual properties are explained in terms of the computed electronic structure, and the results show promise for the development of next-generation photoconducting devices in optoelectronic information science and technology.

关键词： first-principles electronic structure ZnO doping

Theoretical investigation on the electronic structure,elastic properties, and intrinsic hardness of Si2N20

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第6期21卷 421-430页

作者：丁迎春陈敏高秀英蒋孟衡 College of Optoelectronics Technology Chengdu University of Information TechnologyChengdu 610225China

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli （bulk modulus, Young’s mod-ulus, and shear modulus） are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.

关键词： elastic property Vickers hardness electronic structure

First-principles theory on electronic structure and floatability of spodumene

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2014年第6期33卷 742-748页

作者： Gui-Chun He Hua-Mei Xiang Wei Jiang Qian Kang Jian-Hua Chen Faculty of Resource and Environmental Engineering Jiangxi University of Science and Technology College of Resources and Metallurgy Guangxi University

The band structure, density of states, Mulliken populations, and frontier orbital of spodumene crystal were calculated using the first-principles method based on the density functional theory（DFT） and further analyzed in detail. The calculation results reveal that the O in spodumene is the most active and easily links with H＋in the water, but the active Li is very low, so it is better to add activator to increase the concentrate grade and recovery rate of spodumene in the flotation process. Si–O bonds in spodumene crystal are mainly covalent, since the covalency of Al–O bonds is stronger than that of Li–O bonds,and minerals dissociate along the weakest Li–O bonds. In addition, the study of the frontier orbital indicates that both O and Si atoms have large contribution to the frontier orbital in the spodumene crystal. Oleate and dodecylamine are used as the collectors of spodumene. The results contribute to the understanding of crystal structures of spodumene, and can be used in guiding related practical applications.

关键词： Spodumene electronic structure Floatability First-principles method Frontier orbital

Effects of N-doping concentration on the electronic structure and optical properties of N-doped β-Ga_2O_3

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第6期21卷 431-436页

作者：张丽英闫金良张易军李厅 School of Physics Ludong University

The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most stable structure for the smallest formation energy.After N-doping,the charge density distribution significantly changes,and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level.The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration.The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.

关键词： first-principles p-type β-Ga2O3 N-doped electronic structure optical properties