Interaction between impurity nitrogen and tungsten: a first-principles investigation |
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Authors: | Liu Yue-Lin Jin Shuo and Zhang Ying |
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Affiliation: | Department of Physics, Yantai University, Yantai 264005, China;Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191, China;Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191, China |
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Abstract: | We investigate the stability, diffusion, and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method, and find that a single nitrogen atom is energetically favourable for sitting at the octahedral interstitial site. A nitrogen atom prefers to diffuse between the two nearest neighboring octahedral interstitial sites with a diffusion barrier of 0.72 eV. The diffusion coefficient is determined as a function of temperature and expressed as D(N)=1.66×10-7exp (-0.72/kT). The solubility of nitrogen is estimated in intrinsic tungsten in terms of Sieverts' law. The concentration of the nitrogen impurity is found to be 4.82×10-16 Å-3 at a temperature of 600 K and a pressure of 1 Pa. A single nitrogen atom can easily sit in an off-vacancy-centre position close to the octahedral interstitial site. There exists a strong attraction between nitrogen and a vacancy with a large binding energy of 1.40 eV. We believe that these results can provide a good reference for the understanding of the behaviour of nitrogen in intrinsic tungsten. |
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Keywords: | tungsten nitrogen diffusion first-principles |
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