Journal of the Physical Society of Japan
In this study, we implement first-principles calculation to study the physical and chemical properties of two-dimensional (2D) hexagonal crystals. The ab initio results of the crystallographic, elastic, and electronic band-gap parameters of C, Si, Ge, BN, CN, SiN, and SiC monolayers are presented. Similarly to graphene, CN and BN are among compounds with the highest 2D elasticity. The in-plane elastic moduli of Si and Ge monolayers are relative small. C, Si, and Ge monolayers are semimetal. All the four binary 2D crystals are semiconductors with wide band gaps. Two typical 2D hexagonal lattice structures, i.e., sp(2) flat and sp(3) rumpled configurations, are classified. The orbital sp(2)-hybridization in graphene and 2D BN is verified by angular-momentum projected atomic density of state calculation. 2D SiC is basically in sp(2)-hybridization. The orbital hybridization of Si, Ge, CN, and SiN monolayers is of the sp(3)-type on the whole. In view of the structural and chemical features of these monolayers, different methods for the experimental preparation of 2D crystals are suggested.
关键词:
2D crystals;orbital hybridization;elastic moduli;first-principles;calculation;iii-v compounds;elastic-constants;silicon-nitride;graphene;pseudopotentials;membranes;graphite;phase
Dangguo LI
金属学报(英文版)
The chemical composition and semi-conductive properties of passive film on nickel-based alloy (G3 alloy) in bicarbonate/carbonate buffer solution were investigated by Auger spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectra (EIS) and Mott-Schottky plot. AES and XPS results showed that the passive film appeared double-layer, in which the inner film was composed of nickel oxide, the mixed nickel-chromium-molybdenum-manganese oxides were the major component of the outer film. The electrochemical results revealed that the factors including frequency, potential, time, temperature and pH value can affect the semi-conductive property, the doping densities decreased with increasing potential and pH value, prolonging time, and decreasing temperature. According to the above results, it can be concluded that the film protection on the substrate enhanced with increasing potential and pH value, prolonging time, and decreasing temperature.
关键词:
Nickel-based alloy
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俄歇分析
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X-射线光电子能谱
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电化学阻抗谱
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Mott-Schottky曲线
Physica Status Solidi B-Basic Research
The perturbation formulae of EPR g-factors g(i) (i = x, y, z) and hyperfine constants Ai for a 3d(7) (Co2+) ion at a rhombic octahedral site in a crystal are established from a cluster approach. In these formulae, the contributions from the covalency effect, the configuration interaction and the rhombic crystal field are considered and the parameters used in the calculation of EPR parameters. except the core polarization constant x in the calculation of Al, can be estimated from the optical spectra and the structure data of the studied system. From these formulae, the EPR parameters g(i) and A(i) for the rhombic Co2+-V-Ag centre in AgCl are reasonably explained by considering suitable rhombic distortion and so the microstructure of this rhombic centre is obtained.
关键词:
superposition model;crystals
Physica Status Solidi B-Basic Research
The EPR g-factors g(\\), g(perpendicular to) and hyperfine structure constants A(\\), A(perpendicular to) for a tetragonal Co2+ centre, i.e.. Co(H2O)(2)Cl-4 centre, in NH4Cl crystal are calculated from the perturbation formulas based on a cluster approach. In these formulas, the parameters related to the contributions from the configuration interaction. the covalency effect and the low-symmetry crystal field can be obtained from the optical spectra and the structural model and data of the studied system. The core polarization constant it in the calculation formulas of hyperfine constants is used as an adjustable parameter. The calculated results are in good agreement with the observed values.
关键词:
superposition model;centers;resonance;ions;cr3+
L.P. Karjalainen
,
M.C. Somani
,
S.F. Medina
金属学报(英文版)
The analysis of numerous experimental equations published in the literature reveals a
wide scatter in the predictions for the static recrystallization kinetics of steels. The
powers of the deformation variables, strain and strain rate, similarly as the power
of the grain size vary in these equations. These differences are highlighted and the
typical values are compared between torsion and compression tests. Potential errors
in physical simulation testing are discussed.
关键词:
physical simulation
,
null
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null
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null
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null
