Ab initio studies of niobium defects in uranium

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Uranium (U), with the addition of small amount of niobium (Nb), is stainless. The Nb is fully miscible with the high temperature phase of U and tends to segregate upon cooling below 647 C. The starting point of segregation is the configuration of Nb substitutional or interstitial defects. Using density-functional-theory based ab initio calculations, the authors find that the formation energy of a single vacancy is 1.08 eV, that of Nb substitution is 0.59 eV, that of Nb interstitial at octahedral site is 1.58 eV, and that of Nb interstitial at tetrahedral site is 2.35 eV; all with reference to ... continued below

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Xiang, S; Huang, H & Hsiung, L June 1, 2007.

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Uranium (U), with the addition of small amount of niobium (Nb), is stainless. The Nb is fully miscible with the high temperature phase of U and tends to segregate upon cooling below 647 C. The starting point of segregation is the configuration of Nb substitutional or interstitial defects. Using density-functional-theory based ab initio calculations, the authors find that the formation energy of a single vacancy is 1.08 eV, that of Nb substitution is 0.59 eV, that of Nb interstitial at octahedral site is 1.58 eV, and that of Nb interstitial at tetrahedral site is 2.35 eV; all with reference to a reservoir of {gamma} phase U and pure Nb. The formation energy of Nb defects correlates with the local perturbation of electron distribution; higher formation energy to larger perturbation. Based on this study, Nb atoms thermodynamically prefer to occupy substitutional sites in {gamma} phase U, and they prefer to be in individual substitutional defects than clusters.

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PDF-file: 17 pages; size: 1.8 Mbytes

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  • Journal Name: Journal of Nuclear Materials, vol. 375, N/A, March 30, 2008, pp. 113; Journal Volume: 375

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  • Report No.: UCRL-JRNL-231451
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 942031
  • Archival Resource Key: ark:/67531/metadc901679

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • June 1, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Nov. 22, 2016, 2:20 p.m.

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Xiang, S; Huang, H & Hsiung, L. Ab initio studies of niobium defects in uranium, article, June 1, 2007; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc901679/: accessed October 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.