A first principles study of constitutional and thermal defects in D8m-Si3Nb5 |
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| Authors: | Catherine Colinet Jean-Claude Tedenac |
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| Institution: | 1. Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 38402 Saint Martin d''Hères Cedex, France;2. Institut de Chimie Moléculaire et des Matériaux I.C.G., UMR-CNRS 5253, Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5, France;1. Computer Network Information Center, Chinese Academy of Sciences, Beijing 100190, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. General Research Institute for Nonferrous Metals, Beijing 100088, China;4. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China;5. University of Science and Technology of China, Hefei 230026, China;1. Key Laboratory for Organic Electronics & Information Displays (KLOEID), Institute of Advanced Materials (IAM), School of Materials Science and Engineering (SMSE), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China;2. School of Opto-Electronic Engineering, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China;3. School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, PR China;1. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA;2. US Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-B, Aberdeen Proving Ground, MD 21005, USA;3. Materials Science Division, US Army Research Office, Research Triangle Park, NC 27709, USA;4. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China |
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| Abstract: | First principles calculations of point-defect enthalpies of formation are performed in the D8m-Si3Nb5 compound. Four sublattices are introduced to account for the D8m structure. Based on a statistical–thermodynamic model, the defect concentrations are calculated as function of temperature and deviation from stoichiometry. For the stoichiometric composition, all the point-defect atomic concentrations remain very low even at the compound melting temperature. In the Si-rich D8m-Si3Nb5, the constitutional defects are Si antisites on the Nb 4b sites of the D8m structure. The thermal defects are Si antisites on the 16k sites of the D8m structure, but their concentration remains very small even at high temperature. In the Nb-rich D8m-Si3Nb5, the constitutional defects are Nb antisites on the 8h Si positions. The formation Gibbs energy of the D8m-Si3Nb5 phase as well as the Si and Nb chemical potentials are obtained as function of the deviation from stoichiometry for various temperatures. The extension of the one-phase domain of D8m-Si3Nb5 in the Si–Nb phase diagram is discussed. |
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