Papers by Keyword: Vacancy

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Authors: M.V. Magnitskaya, E.T. Kulatov, A.A. Titov, Y.A. Uspenskii, E.G. Maksimov, S.V. Popova, V.V. Brazhkin
Abstract: We report on ab initio density-functional calculations of a novel spintronics-related compound CrGa2Sb2 recently synthesized under high pressure. The effect of Cr deficiency on the electronic, magnetic and optical properties of CrGa2Sb2 is considered. New X-ray structural measurements up to high pressure of 9 GPa are presented.
Authors: Xavier Sauvage
Abstract: Concentration gradients resulting from long range diffusion during Severe Plastic Deformation (SPD) have been investigated with the 3D Atom Probe technique (3D-AP). First, in a pearlitic steel where alloying elements (Mn, Si and Cr) are partitioned between the ferrite and carbides in the non-deformed state. After processing by High Pressure Torsion (HPT), they are homogeneously distributed in the nanostructure, indicating that long range diffusion occurred along with the dissolution of carbides. 3D-AP data of a Cu-Fe composite processed by HPT show as well a significant interdiffusion of Cu and Fe, probably promoted by additional vacancies. On the basis of these experimental data, and using the theory described for irradiated materials, vacancy fluxes and vacancy production rates were estimated assuming that new vacancies are continuously produced and eliminated on grain boundaries.
Authors: E. Sörman, Nguyen Tien Son, W.M. Chen, Christer Hallin, J. Lennart Lindström, Erik Janzén
Authors: Ke Tong, Fei Ye, Ya Kun Wang, Feng Zhou
Abstract: The preferential sites for vacancies on a series of symmetric tilt grain boundaries in copper have been investigated by molecular dynamics simulation. The regularity of preferential sites for vacancies on these boundaries can be described by the structural unit model. This is essential because of the correspondence between the geometries of the structural units and the local stress field. The vacancies are energetically preferred at the sites with relatively large tensile stress, and these sites are the corner sites of the structural units. Moreover, these preferential sites are mainly related to the structural unit types irrespective of which grain boundary that the structure units locate in. Therefore, the preferential sites for vacancies on various grain boundaries formed by combinations of certain structural units can be readily described and predicted by the structural unit model.
Authors: J. del Río, N. de Diego, F. Plazaola, P. Moser
Authors: Meng Liu, Jakub Čížek, Cynthia S.T. Chang, John Banhart
Abstract: Early stages of clustering in quenched Al-Mg-Si alloys during natural ageing were studied by positron annihilation lifetime spectroscopy utilizing its unique sensitivity to electron density differences in various atomic defects. Two different positron trapping sites could be identified, one related to a vacancy-type defect, the other to solute clusters. The first trap is deep, i.e. irreversibly traps positrons, the second shallow, from which positrons can escape, which creates the signature of a temperature-dependent positron lifetime. During the first 80 min of NA, the vacancy-related contribution decreases, while the solute clusters increasingly trap positrons, thus reflecting their continuous growth and power to trap positrons. Coincident Doppler broadening spectroscopy of the annihilation radiation shows that the annihilation sites are Si-rich after quenching but contain more Mg after 70 min.
Authors: Amitava Ghorai
Abstract: A Brief Sketch of Different Models for the Calculation of Defect Parameters in Metals and Alloys, Comparison of Data and Limitations Has Been Reviewed here; Especially Relaxations due to a Vacancy Type of Point Defect, its Formation, Migration, Activation Energies and Related other Parameters Based upon the Present Experimental Status. the Models Reviewed Are the Bond Model, Continuum Model, Semi-Discrete Model, Jellium Model, Thermodynamic Model, Lattice Statics Model, Atomistic Continuum Model and Pseudopotential Model. the Main Thrust Concerns the Last Model. the Taylor, Vashishta and Singwi, Harrison, Kleinmann and King and Kutler Form of Exchange and Correlation Function Are Almost Similar, Give Moderate Results and May Be Trusted for Better Results.
Authors: Wei Qing Wang, Wei Hua Wang, Yu Hua Yan
Abstract: The existence of holes in vehicle object makes it difficult to extract the feature. existing hole-filling method are capable of filling holes on small and smooth regions of a object, for large holes whit complex boundaries or in curved region in vehicle object, they may not obtain the satisfactory results. For resolving this problem, a novel hole-filling algorithm based on horizontal scan line was proposed to fill arbitrary holes in vehicle object obtained from vehicle image. Experiments show that the algorithm has good performance and efficiency, and in the filling processing, the feature of the area and perimeter of an object can be obtained at the same time.
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