检索结果-南通市图书馆

First-principle study on the surface atomic relaxation properties of sphalerite

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2012年第9期19卷 775-781页

作者： Jian Liu Shu-ming Wen Yong-jun Xian Shao-jun Bai Xiu-min Chen Faculty of Land Resource Engineering Kunming University of Science and Technology Kunming 650093 China National Engineering Laboratory of Vacuum Metallurgy Kunming University of Science and Technology Kunming 650093 China

The surface properties of sphalerite （ZnS） were theoretically investigated using first principle calculations based on the density functional theory （DFT）. DFT results indicate that both the （110） and the （220） surfaces of sphalerite undergo surface atom relaxation after geometry optimization, which results in a considerable distortion of the surface region. In the normal direction, i.e., perpendicular to the sur- face, S atoms in the first surface layer move outward from the bulk （dl）, whereas Zn atoms move toward the bulk （d2）, forming an S-enriched surface. The values of these displacements are 0.003 nm for dl and 0.021 nm for d2 on the （110） surface, and 0.002 nm for dl and 0.011 nm for d2 on the （220） surface. Such a relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. X-ray photoelectron spectroscopic （XPS） analysis provides the evidence for the S-enriched surface. A polysulphide （S n^2- ） surface layer with a bind- ing energy of 163.21 eV is formed on the surface of sphalerite after its grinding under ambient atmosphere. This S-enriched surface and the S 2- surface layer have important influence on the flotation properties ofsphalerite. Keywords：

关键词： sphalerite surface relaxation density fimctional theory froth flotation

surface deformation-dependent mechanical properties of bending nanowires:an ab initio core-shell model

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 219-232页

作者： Ye XIAO J.SHANG L.Z.KOU Chun LI School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an710072China School of Mechanical Medical and Process EngineeringQueensland University of TechnologyBrisbaneQLD4000Australia

An ab initio core-shell model is proposed to evaluate the surface effect in bending nanowires,in which the elastic modulus depends on the surface relaxation and deformation induced by external *** using first-principles calculations based on the density functional theory(DFT),the surface and bulk properties are calculated for Ag,Pb,and Si *** obtained theoretical predictions of the effective Young’s modulus of nanowires agree well with the experimental data,which shows that the fixed-fixed nanowire is stiffened and the cantilevered nanowire is softened as the characteristic size of the cross section ***,the contrastive analysis on the two kinds of nanowires demonstrates that increasing the nanowire aspect ratio would enhance the surface *** present results could be helpful for understanding the size effect in nanowires and designing nanobeam-based devices in nanoelectromechanical systems(NEMSs).

关键词： surface effect density functional theory(DFT) surface relaxation surface stress nanowire

Multiscale energy density algorithm and application to surface structure of Ni matrix of superalloy

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第9期27卷 486-492页

作者：孙敏王崇愚刘吉平 School of Material Science and Engineering Beijing Institute of Technology Department of Physics Tsinghua University

Multiscale materials modeling as a new technique could offer more accurate predictive capabilities. The most active area of research for multiscale modeling focuses on the concurrent coupling by considering models on disparate scales simultaneously. In this paper, we present a new concurrent multiscale approach, the energy density method(EDM), which couples the quantum mechanical(QM) and the molecular dynamics(MD) simulations simultaneously. The coupling crossing different scales is achieved by introducing a transition region between the QM and MD domains. In order to construct the energy formalism of the entire system, concept of site energy and weight parameters of disparate scales are *** EDM is applied to the study of the multilayer relaxation of the Ni(001) surface structure and is validated against the periodic density functional theory(DFT) calculations. The results show that the concurrent EDM could combine the accuracy of the DFT description with the low computational cost of the MD simulation and is suitable to the study of the local defects subjected to the influence of the long-range environment.

关键词： first-principles calculation molecular dynamics surface relaxation nickel

First-principles of wurtzite ZnO(0001) and (0001)surface structures

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Semiconductors 2010年第8期31卷 1-5页

作者：张宇飞郭志友高小奇曹东兴戴云宵赵洪涛 Institute of Optoelectronic Material and Technology South China Normal University

The surface structures ofwurtzite ZnO（0001） and（0001） surfaces are investigated by using a first-principles calculation of plane wave ultra-soft pseudo-potential technology based on density functional theory（DFT）.The calculated results reveal that the surface energy of ZnO-Zn is bigger than that of ZnO-O,and the ZnO-Zn surface is more unstable and *** two surfaces are apt to relax inward,but the contractions of the ZnO-Zn surface are smaller than the ZnO-O *** to the dispersed Zn4s states and the states of stronger hybridization between the Zn and O atoms,the ZnO-Zn surface shows n-type conduction,while the O2p dangling-bond bands in the upper part of the valence cause the ZnO-O surface to have p-type *** above results are broadly consistent with the experimental results.

关键词： ZnO(0001) and(0001) surface energy surface relaxation electronic structures

THE SIZE-DEPENDENT ELASTIC PROPERTIES OF NANOFILM WITH surface EFFECTS

在线全文

学校读者我要写书评

暂无评论

THE SIZE-DEPENDENT ELASTIC PROPERTIES OF NANOFILM WITH SURFA...