First principles study of substituents in KTaO{sub 3}

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The structural properties, energetics, and dynamics of Ca{sup 2+} and Mn{sup 2+} substituents in KTaO{sub 3} are investigated from first principles. It is found that Ca substitutes for both K and Ta ions. Oxygen vacancies bind to isolated Ca ions residing at Ta-sites, causing off-center Ca displacement and forming large dipoles. There is also evidence that oppositely charged defects may cluster together. The calculations predict that the activation energy for dipole reorientation via oxygen vacancy hopping within the first neighbor shell of Ta-substituting Ca or Mn exceeds 2 eV. On the other hand, Mn{sup 2+} substituting at the K-site displaces ... continued below

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33 p.

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LEUNG,KEVIN May 17, 2000.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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The structural properties, energetics, and dynamics of Ca{sup 2+} and Mn{sup 2+} substituents in KTaO{sub 3} are investigated from first principles. It is found that Ca substitutes for both K and Ta ions. Oxygen vacancies bind to isolated Ca ions residing at Ta-sites, causing off-center Ca displacement and forming large dipoles. There is also evidence that oppositely charged defects may cluster together. The calculations predict that the activation energy for dipole reorientation via oxygen vacancy hopping within the first neighbor shell of Ta-substituting Ca or Mn exceeds 2 eV. On the other hand, Mn{sup 2+} substituting at the K-site displaces off center along the (100) direction, also forming a dipole. This dipole can reorient via Mn hopping motion with an activation energy of {approximately} 0.18 eV, in reasonable agreement with experiments. The authors argue that, in general, metal ion hopping at the A-site, not oxygen vacancy hopping, is responsible for the small activation energies found in experiments.

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33 p.

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OSTI as DE00755614

Medium: P; Size: 33 pages

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  • Journal Name: Physical Review B; Other Information: Submitted to Physical Review B

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  • Report No.: SAND2000-1254J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 755614
  • Archival Resource Key: ark:/67531/metadc703775

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  • May 17, 2000

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  • Sept. 12, 2015, 6:31 a.m.

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  • April 12, 2017, 1:29 p.m.

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LEUNG,KEVIN. First principles study of substituents in KTaO{sub 3}, article, May 17, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc703775/: accessed April 26, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.