Structure of Cerium Phosphate Glasses: Molecular Dynamics Simulation

Authors

  • Jincheng Du,

    Corresponding author
    1. Department of Materials Science and Engineering, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203
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    • *Member, American Ceramic Society.

  • Leopold Kokou,

    1. Department of Materials Science and Engineering, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203
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    • *Member, American Ceramic Society.

  • Jennifer L. Rygel,

    1. Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802
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    • *Member, American Ceramic Society.

  • Yongsheng Chen,

    1. Department of Energy and Mineral Engineering, Earth and Mineral Sciences Energy Institute, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802
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  • Carlo G. Pantano,

    1. Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802
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    • **Fellow, American Ceramic Society.

  • Robert Woodman,

    1. Infoscitex Inc., Waltham, Massachusetts 02451
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    • *Member, American Ceramic Society.

  • James Belcher

    1. Infoscitex Inc., Waltham, Massachusetts 02451
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  • L.-Q. Chen—contributing editor

  • Presented in part at the 2010 Glass & Optical Materials Division Annual Meeting, Corning, NY, May 18, 2010 (Paper number GOMD-SII-013-2010).

  • This work was financially supported by Air Force Research Laboratory (AFRL) SBIR phase II.

†Author to whom correspondence should be addressed. e-mail: jincheng.du@unt.edu

Abstract

We performed molecular dynamics (MD) simulations of the structure and properties of cerium-containing phosphosilicate, aluminophosphate, and aluminophosphosilicate glasses based on recent spectroscopic data that revealed 95% of cerium ions in such glasses are Ce3+. New Ce3+- and Ce4+-O2− potentials were developed and used in the MD simulations of these cerium-containing glasses with mixed glass formers. The local environments around cerium ions and network-forming cations, the medium range structure including glass-forming network Qn distribution, clustering, and second coordination shell around cerium ions have been carefully characterized. The results showed a longer Ce–O bond length and larger coordination number for Ce3+ than Ce4+ (2.48 and 6.4 vs. 2.24Å and 5.8, respectively). Around 5% of Si4+ ions were found to be in fivefold and sixfold coordination states in cerium phosphosilicate glasses, rather than the usual fourfold in silicate glasses. At the same time, the silicon–oxygen polyhedra were highly polymerized (over 80% of Q4) due to the presence of phosphorus oxide. Aluminum ions were found to be coordinated by four-, five-, and six oxygen ions, with an average coordination number of around 4.2. In both oxidation states, cerium ions were found to be preferentially surrounded by phosphorus–oxygen tetrahedra, which form a kind of solvation shell around them. The preference of network-forming cations around cerium ions in the second coordination shell was found to decrease in the sequence phosphorus, aluminum, silicon.

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