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A. Kulińska M. Uhrmacher R. Dedryvère A. Lohstroh K.P. Lieb J.-C. Jumas 《Journal of solid state chemistry》2004,177(1):109-118
LixIn2S3 was electrochemically prepared with different small amounts x of lithium (0?x?0.13) in order to maintain the initial crystallographic structure of the thiospinel In2S3. About 1012 radioactive 111In ions have been implanted into these samples at 400 keV to perform PAC experiments in the temperature range from 10 to 773 K. The results are compared to previous experiments with undoped In2S3 samples. According to the structure of In2S3 in the β-phase, which belongs to the I41/amd space group having a unit cell with 32 In and 48 S atoms and the cell parameters α=7.61 Å and c=32.28 Å, three different electric field gradients were observed. Within two different temperature ranges dynamical EFGs occur, which are clearly influenced by the insertion of Lithium. The strong dependence of one EFG on the Li concentration x can be correlated to the effective charge of the In ions. This correlation is discussed with respect to XRD analyses of the LixIn2S3 samples and to XANES measurements on a similar sample. 相似文献
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The electronic structure of substitutional non-magnetic impurities Cu, Ag, Cd, Mg, Zn, Ga, In, Ge, Si and Sn in Al is studied
using density functional theory. A simple physical model is proposed to calculate the effective charges on impurities in trivalent
metal Al. A linear relation is found between the effective charges on impurities and impurity vacancy capture radii. The spherical
solid model (SSM) is used to account for discrete nature of the host. The impurity-induced change in charge density, scattering
phase shifts, host-impurity potential, residual resistivity and impurity self-energy are calculated. Higher order scattering
phase shifts are found significant and the host-impurity potential is found proportional to effective charge on impurity in
its vicinity. The self-consistently calculated potential is used to calculate the electric field gradients (EFGs) at the first
and second nearest neighbours (1NNs, 2NNs) of impurity. The calculated values are in agreement with the experimental results. 相似文献
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Ooms KJ Feindel KW Willans MJ Wasylishen RE Hanna JV Pike KJ Smith ME 《Solid state nuclear magnetic resonance》2005,28(2-4):125-134
Results from a solid-state 139La NMR spectroscopic investigation of the anhydrous lanthanum(III) halides (LaX3; X=F, Cl, Br, I) at applied magnetic fields of 7.0, 9.4, 11.7, 14.1, and 17.6 T are presented and highlight the advantages of working at high applied magnetic field strengths. The 139La quadrupolar coupling constants are found to range from 15.55 to 24.0 MHz for LaCl3 and LaI3, respectively. The lanthanum isotropic chemical shifts exhibit an inverse halogen dependence with values ranging from −135 ppm for LaF3 to 700 ppm for LaI3, which represents nearly half of the total lanthanum chemical shift range. The spans of the magnetic shielding tensors also vary widely, from 35 to 650 ppm for the solid LaF3 through LaI3. DFT calculations of the 139La electric field gradient and magnetic shielding tensors have been performed and provide a qualitative interpretation of the trends observed experimentally. 相似文献
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This paper uses the element‐free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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An element-free Galerkin (EFG) method for numerical solution of the coupled Schrodinger-KdV equations 下载免费PDF全文
The present paper deals with the numerical solution of the coupled Schrodinger-KdV equations using the elementfree Galerkin (EFG) method which is based on the moving least-square approximation. Instead of traditional mesh oriented methods such as the finite difference method (FDM) and the finite element method (FEM), this method needs only scattered nodes in the domain. For this scheme, a variational method is used to obtain discrete equations and the essential boundary conditions are enforced by the penalty method. In numerical experiments, the results are presented and compared with the findings of the finite element method, the radial basis functions method, and an analytical solution to confirm the good accuracy of the presented scheme. 相似文献
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In the recent decade, the meshless methods have been handled for solving most of PDEs due to easiness of the meshless methods. One of the popular meshless methods is the element-free Galerkin (EFG) method that was first proposed for solving some problems in the solid mechanics. The test and trial functions of the EFG are based on the special basis. Recently, some modifications have been developed to improve the EFG method. One of these improvements is the variational multiscale EFG procedure. In the current article, the shape functions of interpolation moving least squares approximation have been applied to the variational multiscale EFG technique for solving the incompressible magnetohydrodynamics flow. In order to reduce the elapsed CPU time of simulation, we employ a reduced-order model based on the proper orthogonal decomposition technique. The current combination can be referred to as the reduced-order variational multiscale EFG technique. To illustrate the reduction in CPU time used as well as the efficiency of the proposed method, we applied it for the two-dimensional cases. 相似文献
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使用导模法(EFG)生长了多片a面蓝宝石晶体。显微拉曼光谱结合电感耦合等离子体发射光谱(ICP-AES)测试得出晶体的气泡中可能存在含S化合物。晶体表面明显的生长条纹主要与温度、生长速度的波动以及模具的加工精度有关。化学腐蚀分析表明晶体位错密度在4.2×104 cm-2,未存在小角度晶界缺陷,双晶摇摆曲线半峰宽(FWHM)为70.63″。由于采用石墨保温材料,晶体中存在F心与F+色心。晶体在400~3 000 nm波段透过率高于80%,空气中退火后可减弱色心吸收。本文研究结果可为蓝宝石晶体缺陷形成理论研究提供参考,也可为导模法蓝宝石工业生产技术改进提供借鉴。 相似文献