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31.
We present the formation of single-phase Si1−xGex (x=0.2, 0.4, 0.6, and 0.8) alloy nanocrystals dispersed in a SiO2 matrix. The studied samples were prepared by co-sputtering with excess Si1−xGex in SiO2 of approximately 33 at%. Upon heat treatment, crystallization of Si1−xGex alloys was examined by using X-ray diffraction and high-resolution transmission electron microscopy measurements. Single structure of face-centered cubic nanocrystals in a space group Fd-3m was concluded. The average nanocrystal size (from 2 nm to 10 nm) and the lattice constant a of the single-phase Si1−xGex nanocrystals were found to increase with the Ge composition parameter x. Density functional theory-generalized gradient approximation calculation showed the replacement of Ge into the Si sites and vice versa. 相似文献
32.
Pressure dependence of physical properties of GaN/AlN multi-quantum wells (MQWs) was investigated using ab intio calculations. The influence of pressure was divided into two main contributions: pressure affecting the properties of GaN and AlN bulk semiconductors and an influence on systems of polar quantum wells deposited on various substrates. An influence of hydrostatic, uniaxial, and tetragonal strain on the crystallographic structure, polarization (piezoelectricity), and the bandgap of the bulk systems is assessed using ab initio calculations. It was shown that when a partial relaxation of the structure is assumed, the tetragonal strain may explain an experimentally observed reduction of pressure coefficients for polar GaN/AlN MQWs. The MQWs were also simulated directly using density functional theory (DFT) calculations. A comparison of these two approaches confirmed that nonlinear effects induced by the tetragonal strain related to lattice mismatch between the substrates and the polar MQWs systems are responsible for a drastic decrease of the pressure coefficients of photoluminescence (PL) energy experimentally observed in polar GaN/AlGaN MQWs. 相似文献
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Numerical Algorithms - The notation of Moore-Penrose inverse of matrices has been extended from matrix space to even-order tensor space with Einstein product. In this paper, we give the numerical... 相似文献
36.
Chen Huang 《Journal of Mathematical Analysis and Applications》2022,505(2):125496
This paper considers the following general form of quasilinear elliptic equation with a small perturbation: where is a bounded domain with smooth boundary and small enough. We assume the main term in the equation to have a mountain pass structure but do not suppose any conditions for the perturbation term . Then we prove the equation possesses a positive solution, a negative solution and a sign-changing solution. Moreover, we are able to obtain the asymptotic behavior of these solutions as . 相似文献
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Numerical Algorithms - In this work, we consider some preconditioning techniques for a class of 3 × 3 block saddle point problems, which arise from finite element methods for solving... 相似文献
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Chen Yue Peng Xihong Fan Xinyue Yu Qing Zhao Guiying Lin Yingbin Li Jiaxin Huang Zhigao 《Journal of Solid State Electrochemistry》2019,23(2):367-377
Journal of Solid State Electrochemistry - A big challenge in the high-performance transition metal oxide anode for lithium-ion batteries (LIBs) is relieving the volume changes during the... 相似文献
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The crystal structure and phase transition temperature of [N(C2H5)4]2CuBr4 are studied using X-ray diffraction and differential scanning calorimetry (DSC); measurements revealed a tetragonal structure and the two phase transition temperatures TC of 204 K and 255.5 K. The structural geometry near TC is discussed in terms of the chemical shifts for 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR) and 13C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups are distinguishable by the 13C NMR spectrum. The molecular motions are discussed in terms of the spin–lattice relaxation times T1ρ in the rotating frame for 1H MAS NMR and 13C CP/MAS NMR. The T1ρ results reveal that the ethyl groups undergo tumbling motion, and furthermore that the ethyl groups are highly mobile. 相似文献