Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids
,
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:
G.B.Hu and Q.B.Yang (Department of Physics
,
Xiangtan University
,
Xiangtan 411105
,
China)(Beijing Laboratory of Electron Microscopy
,
Center for Condensed Matter Physics
,
The Chinese Academy of Sciences
,
P. O. Box 2724
,
Beijing 100080
,
China)
金属学报(英文版)
Excellent results are obtained in structure analysis with jew phases of structure factors by the maximum-entropy method (MEM) for CaGaN PbCO3 and ReBe22 single crystals. The computation time and memory space are minimized by symmetry operations so that structure analysis by the MEM can be carried out with a personal computer.
关键词:
maximum entropy method
,
null
,
null
,
null
Journal of Physical Chemistry B
We have performed quantum-based multiscale simulations to study the initial chemical processes of condensed-phase octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) under shock wave loading. A self-consistent charge density-functional tight-binding (SCC-DFTB) Method Was employed. The results show that the initial decomposition of shocked HMX is triggered by the N-NO2 bond breaking under the low velocity impact (8 km/s). As the shock velocity increases (11 km/s), the homolytic cleavage of the N-NO2 bond is suppressed under high pressure, the C-H bond dissociation becomes the primary pathway for HMX decomposition in its early stages. It is accompanied by a five-membered ring formation and hydrogen transfer from the CH2 group to the -NO2 group. Our simulations suggest that the initial chemical processes of shocked HMX are dependent on the impact velocity, which gain new insights into the initial decomposition mechanism of HMX upon shock loading at the atomistic level, and have important implications for understanding and development of energetic materials.
关键词:
equation-of-state;ab-initio;thermal-decomposition;alpha-hmx;gas-phase;high-pressure;octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine hmx;cyclotetramethylene-tetranitramine;unimolecular decomposition;crystal;structure
Journal of Applied Physics
This article demonstrates, from the theoretical paint off view, chat owing to the phonon-assisted relaxation rate of the excited electron-hole pair's transiting to lower states decreases as the scale of Si particle is reduced, the optically excited electron-hole pair in the nanometer silicon particle with sufficient small scale generally tunnel inter the SiOx layers which enclose the Si particles and recombine radiatively through the luminescence centers there to emit visible Sight rather than recombine radiatively in the Si particles. It is proved also that when the density of the luminescence center is 2.5X10(22)/m(3) the upper limit of the average scale of the nanometer silicon particles in the ensemble capable of emitting red light in room temperature is around 8.7 nm, which is. much bigger than the generally estimated value of 3 nm. (C) 1997 American Institute of Physics.
关键词:
silicon films;light-emission;photoluminescence;mechanism;absorption;layers;nm
