DONG Lianke WANG Xiaowei Institute of Metal Research
,
International Centre for Material Physics
,
Academia Sinica
,
Shenyang
,
China Associate Professor
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang 110015
,
China
金属学报(英文版)
Using gauge field theory of defects,the effective critical extension force in elastic-plastic fracture mechanics was given.The rationality of logarithm of effective extension force as a linear function of the fractal dimensionality of the fracture surface was analyzed in theory. The explanation in approach to studying material toughness using fractal has been clarified.
关键词:
defect gauge field
,
null
,
null
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+
Pramana-Journal of Physics
By calculating the optical spectrum band positions and EPR parameters (g factors, g(parallel to), g(perpendicular to) and zero-field splitting D) by diagonalizing the complete energy matrix of 3d(8) ions in trigonal symmetry, the defect structure of Ni2+ centre in alpha-LiIO3 crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni2+ ion should shift by Delta z approximate to 0.298 angstrom along C-3-axis and the O-2-ions between the Ni2+ ion and Li+ vacancy (V-Li) should be displaced away from the V-Li by Delta x approximate to 0.097 angstrom because of the electrostatic interaction. The results are discussed.
关键词:
Optical spectra;electron paramagnetic resonance;defect structure;Ni2+;alpha-LiIO3.;field;ions;cr3+;temperature;parameters;epr;pressure;model;liio3
Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids
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Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
110015
,
China)
材料科学技术（英文）
The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.
关键词:
Applied Physics Letters
Impedance analysis was employed to study the frequency response characteristics of supercapacitors utilizing single-walled carbon nanotubes (SWNTs) as electrode material. The knee frequency is around 631 Hz for the electrochemically oxidized SWNT supercapacitor, much higher than that of the as-prepared one (around 316 Hz) and the common activated carbon supercapacitor (< 1 Hz). The good frequency response observed in this work is due to the introduction of nanosized mesopores and oxygen-containing groups formed during the electrochemical oxidization of SWNTs. The capacitance of electrochemically oxidized SWNT supercapacitor is 113 F/g, which is much higher than the value of the as-prepared one (20 F/g). (C) 2008 American Institute of Physics.
关键词:
double-layer capacitance;electrochemical capacitors;surface-chemistry;activated carbon;composite;fiber
