First-principles calculation of formation energies and electronic structures of hydrogen defects at tetrahedral and octahedral interstitial sites in pyrochlore-type Y2Ti2O7 oxide

B. Tsuchiya, T. Yamamoto, Kazuhito Ohsawa, G. R. Odette

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Abstract

The formation energies of hydrogen (H) defects at tetrahedral and octahedral interstitial sites in a pyrochlore-type yttrium-titanium oxide (Y2Ti2O7) were calculated using density functional theory. The results were compared with the corresponding energies of H and helium (He) defects in iron (Fe) with a body-centered cubic (bcc) crystal structure and Y2Ti2O7 interstitial and substitutional sites in the matrix. The formation energy of a H defect at a tetrahedral site in Y2Ti2O7 (2.87 eV), which is lower than that at an octahedral site (3.01 eV), was larger than the corresponding energies (0.11, 0.24, and 0.41 eV) at tetrahedral interstitial, octahedral interstitial, and substitutional sites in Fe, respectively. This result indicates that H atoms in nanostructured ferritic alloys, constructed by only bcc Fe containing nanometer-sized Y2Ti2O7 nanofeatures, prefer to occupy tetrahedral interstitial sites in Fe, whereas He atoms prefer to occupy octahedral interstitial sites in Y2Ti2O7. The electron-density distribution and density of states of interstitial H in Y2Ti2O7 reveal an essentially attractive chemical interaction resulting from charge transfers from neighboring O2- anions and surrounding Y3+ and Ti4+ cations, whereas those of interstitial He reveal a repulsive interaction. Therefore, the doping H and He atoms prefer to occupy smaller tetrahedral and larger octahedral sites, respectively.

Original languageEnglish
Pages (from-to)153-159
Number of pages7
JournalJournal of Alloys and Compounds
Volume678
DOIs
Publication statusPublished - Sep 5 2016

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Helium
Oxides
Electronic structure
Hydrogen
Defects
Atoms
Yttrium
Electronic density of states
Titanium oxides
Density functional theory
Anions
Cations
Charge transfer
Negative ions
Iron
Crystal structure
Positive ions
Doping (additives)
pyrochlore

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

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title = "First-principles calculation of formation energies and electronic structures of hydrogen defects at tetrahedral and octahedral interstitial sites in pyrochlore-type Y2Ti2O7 oxide",
abstract = "The formation energies of hydrogen (H) defects at tetrahedral and octahedral interstitial sites in a pyrochlore-type yttrium-titanium oxide (Y2Ti2O7) were calculated using density functional theory. The results were compared with the corresponding energies of H and helium (He) defects in iron (Fe) with a body-centered cubic (bcc) crystal structure and Y2Ti2O7 interstitial and substitutional sites in the matrix. The formation energy of a H defect at a tetrahedral site in Y2Ti2O7 (2.87 eV), which is lower than that at an octahedral site (3.01 eV), was larger than the corresponding energies (0.11, 0.24, and 0.41 eV) at tetrahedral interstitial, octahedral interstitial, and substitutional sites in Fe, respectively. This result indicates that H atoms in nanostructured ferritic alloys, constructed by only bcc Fe containing nanometer-sized Y2Ti2O7 nanofeatures, prefer to occupy tetrahedral interstitial sites in Fe, whereas He atoms prefer to occupy octahedral interstitial sites in Y2Ti2O7. The electron-density distribution and density of states of interstitial H in Y2Ti2O7 reveal an essentially attractive chemical interaction resulting from charge transfers from neighboring O2- anions and surrounding Y3+ and Ti4+ cations, whereas those of interstitial He reveal a repulsive interaction. Therefore, the doping H and He atoms prefer to occupy smaller tetrahedral and larger octahedral sites, respectively.",
author = "B. Tsuchiya and T. Yamamoto and Kazuhito Ohsawa and Odette, {G. R.}",
year = "2016",
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TY - JOUR

T1 - First-principles calculation of formation energies and electronic structures of hydrogen defects at tetrahedral and octahedral interstitial sites in pyrochlore-type Y2Ti2O7 oxide

AU - Tsuchiya, B.

AU - Yamamoto, T.

AU - Ohsawa, Kazuhito

AU - Odette, G. R.

PY - 2016/9/5

Y1 - 2016/9/5

N2 - The formation energies of hydrogen (H) defects at tetrahedral and octahedral interstitial sites in a pyrochlore-type yttrium-titanium oxide (Y2Ti2O7) were calculated using density functional theory. The results were compared with the corresponding energies of H and helium (He) defects in iron (Fe) with a body-centered cubic (bcc) crystal structure and Y2Ti2O7 interstitial and substitutional sites in the matrix. The formation energy of a H defect at a tetrahedral site in Y2Ti2O7 (2.87 eV), which is lower than that at an octahedral site (3.01 eV), was larger than the corresponding energies (0.11, 0.24, and 0.41 eV) at tetrahedral interstitial, octahedral interstitial, and substitutional sites in Fe, respectively. This result indicates that H atoms in nanostructured ferritic alloys, constructed by only bcc Fe containing nanometer-sized Y2Ti2O7 nanofeatures, prefer to occupy tetrahedral interstitial sites in Fe, whereas He atoms prefer to occupy octahedral interstitial sites in Y2Ti2O7. The electron-density distribution and density of states of interstitial H in Y2Ti2O7 reveal an essentially attractive chemical interaction resulting from charge transfers from neighboring O2- anions and surrounding Y3+ and Ti4+ cations, whereas those of interstitial He reveal a repulsive interaction. Therefore, the doping H and He atoms prefer to occupy smaller tetrahedral and larger octahedral sites, respectively.

AB - The formation energies of hydrogen (H) defects at tetrahedral and octahedral interstitial sites in a pyrochlore-type yttrium-titanium oxide (Y2Ti2O7) were calculated using density functional theory. The results were compared with the corresponding energies of H and helium (He) defects in iron (Fe) with a body-centered cubic (bcc) crystal structure and Y2Ti2O7 interstitial and substitutional sites in the matrix. The formation energy of a H defect at a tetrahedral site in Y2Ti2O7 (2.87 eV), which is lower than that at an octahedral site (3.01 eV), was larger than the corresponding energies (0.11, 0.24, and 0.41 eV) at tetrahedral interstitial, octahedral interstitial, and substitutional sites in Fe, respectively. This result indicates that H atoms in nanostructured ferritic alloys, constructed by only bcc Fe containing nanometer-sized Y2Ti2O7 nanofeatures, prefer to occupy tetrahedral interstitial sites in Fe, whereas He atoms prefer to occupy octahedral interstitial sites in Y2Ti2O7. The electron-density distribution and density of states of interstitial H in Y2Ti2O7 reveal an essentially attractive chemical interaction resulting from charge transfers from neighboring O2- anions and surrounding Y3+ and Ti4+ cations, whereas those of interstitial He reveal a repulsive interaction. Therefore, the doping H and He atoms prefer to occupy smaller tetrahedral and larger octahedral sites, respectively.

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