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 favourabl...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 a.s D（N） = 1.66 ~ 10-7 exp（-O.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 /~ 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.展开更多
In terms of first-principles investigation of H-tungsten (W) interaction,we reveal a generic optimal electron density mechanism for H on W(110) surface and at a vacancy in W.Both the surface and vacancy internal surfa...In terms of first-principles investigation of H-tungsten (W) interaction,we reveal a generic optimal electron density mechanism for H on W(110) surface and at a vacancy in W.Both the surface and vacancy internal surface can provide a quantitative optimal electron density of~0.10electron/(A)3 for H binding to make H stability.We believe that such a mechanism is also applicable to other surfaces such as W( 100) surface because of the (100) surface also providing an optimal electron density for H binding,and further likely actions on other metals.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50871009 and 51101135)the National Magnetic Confinement Fusion Program,China(Grant No.2009GB106003)
文摘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 a.s D（N） = 1.66 ~ 10-7 exp（-O.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 /~ 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.
基金Supported by the National Natural Science Foundation of China under Grant No 51101135the National Fusion Project of China for ITER under Grant No 2009GB106003.
文摘In terms of first-principles investigation of H-tungsten (W) interaction,we reveal a generic optimal electron density mechanism for H on W(110) surface and at a vacancy in W.Both the surface and vacancy internal surface can provide a quantitative optimal electron density of~0.10electron/(A)3 for H binding to make H stability.We believe that such a mechanism is also applicable to other surfaces such as W( 100) surface because of the (100) surface also providing an optimal electron density for H binding,and further likely actions on other metals.
