Modeling of the phase evolution in Mg1-xAlxB2 (0<x<0.5) and its experimental signatures

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Despite the chemical and structural simplicity of MgB{sub 2}, at 39 K this compound has the highest known {Tc} of any binary compound. Electron doping by substituting Al for Mg leads to decreasing Tc and the observed concentration dependent rate of decrease has been proposed to arise from the non-ideal character of MgB{sub 2}-AIB{sub 2} solid solutions, which derives from the existence of an ordered Mg{sub 0.5}Al{sub 0.5}B{sub 2} compound. Heterogeneous nano-scale structure patterns in solid solutions have emerged as an important concept for complex materials, ranging from actinide alloys and oxides to high-temperature cuprate superconductors and mallganite-based materials exhibiting ... continued below

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11965

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Andersson, Anders David; Casillas, Luis; Lezama Pacheco, Juan & Conradson, Steven D January 1, 2009.

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Despite the chemical and structural simplicity of MgB{sub 2}, at 39 K this compound has the highest known {Tc} of any binary compound. Electron doping by substituting Al for Mg leads to decreasing Tc and the observed concentration dependent rate of decrease has been proposed to arise from the non-ideal character of MgB{sub 2}-AIB{sub 2} solid solutions, which derives from the existence of an ordered Mg{sub 0.5}Al{sub 0.5}B{sub 2} compound. Heterogeneous nano-scale structure patterns in solid solutions have emerged as an important concept for complex materials, ranging from actinide alloys and oxides to high-temperature cuprate superconductors and mallganite-based materials exhibiting colossal magnetoresistivity. In this work we investigate the formation of structural heterogeneities in Mg{sub 1-x}AI{sub x}B{sub 2}, which take the form of nano-scale AI-AI and AI-Mg domains of different geometry and size, using molecular statics/dynamics simulations and in particular we study the corresponding signatures in diffraction experiments. In order to undertake this task we first derive appropriate Mg-AI-B semi-empirical potentials within the Modified Embedded Atom Method formalism. These potentials are also applied to explore the equilibrium Mg{sub 1-x}AI{sub x}B{sub 2} phase diagram for 0 &lt; x &lt; 0.5. Additionally, density functional theory calculations were utilized to study the influence of heterogeneities on the electronic structure and charge distribution in Mg{sub 1-x}AI{sub x}B{sub 2}.

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11965

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  • Journal Name: Publication in Journal of Physical Chemistry B; Journal Volume: 113; Journal Issue: 35

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  • Report No.: LA-UR-09-00756
  • Report No.: LA-UR-09-756
  • Grant Number: AC52-06NA25396
  • DOI: 10.1021/jp902505r | External Link
  • Office of Scientific & Technical Information Report Number: 956393
  • Archival Resource Key: ark:/67531/metadc934378

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  • January 1, 2009

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  • Nov. 13, 2016, 7:26 p.m.

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  • Dec. 12, 2016, 12:24 p.m.

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Andersson, Anders David; Casillas, Luis; Lezama Pacheco, Juan & Conradson, Steven D. Modeling of the phase evolution in Mg1-xAlxB2 (0<x<0.5) and its experimental signatures, article, January 1, 2009; [New Mexico]. (digital.library.unt.edu/ark:/67531/metadc934378/: accessed April 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.