Density-functional study of the La2Zr2O7 low-index surfaces

Mantz, Yves A.; Duan, Yuhua

doi:10.1016/j.susc.2018.04.010

Title: Density-functional study of the La₂Zr₂O₇ low-index surfaces

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Abstract

We report that in order to explain the ability of lanthanum zirconate (La₂Zr₂O₇, LZ) and various doped forms of LZ to function as catalysts, an understanding of LZ surface structures is needed. Accordingly, certain LZ surfaces that are expected to be prevalent in prepared samples of LZ, namely, the low-index (001), (011), and (111) surfaces, are examined at the level of density-functional theory. All possible surface terminations of these surfaces formed by cleaving a perfect LZ crystal, termed ideal surface terminations, are considered, as well as several defective surface terminations of a given surface. Surface energies and surface free energies are computed, and surface phase diagrams (SPDs) of the (001), (011), and (111) surfaces are obtained. From these SPDs, the thermodynamically preferred surface termination of the (001), (011), or (111) surface is concluded to be nonideal over a large range of temperature and oxygen gas partial pressure conditions. This finding is unchanged if the SPDs are determined more accurately by taking into account certain vibrational contributions obtained from computed phonon dispersions. Additionally, a way to use results to characterize the surfaces of synthesized LZ crystallites is discussed, but the shapes or dimensions of the crystallites first need to be obtained.

Authors:

Mantz, Yves A. ^[1];

^[2]

National Energy Technology Lab. (NETL), Morgantown, WV (United States)
National Energy Technology Lab. (NETL), Pittsburgh, PA (United States)

Publication Date:: 2018-04-26

Research Org.:: National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)

Sponsoring Org.:: USDOE Office of Fossil Energy (FE)

OSTI Identifier:: 1582394

Report Number(s):: NETL-PUB-22200
Journal ID: ISSN 0039-6028

Resource Type:: Accepted Manuscript

Journal Name:: Surface Science

Additional Journal Information:: Journal Volume: 689; Journal Issue: C; Journal ID: ISSN 0039-6028

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; La2Zr2O7; Pyrochlore oxide; Surface free energy; Density-functional theory

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                    Mantz, Yves A., and Duan, Yuhua. Density-functional study of the La2Zr2O7 low-index surfaces.  United States: N. p., 2018. 
Web.  doi:10.1016/j.susc.2018.04.010.

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                    Mantz, Yves A., & Duan, Yuhua. Density-functional study of the La2Zr2O7 low-index surfaces.  United States.  https://doi.org/10.1016/j.susc.2018.04.010

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                    Mantz, Yves A., and Duan, Yuhua. Thu .  
"Density-functional study of the La2Zr2O7 low-index surfaces".  United States.  https://doi.org/10.1016/j.susc.2018.04.010.  https://www.osti.gov/servlets/purl/1582394.

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@article{osti_1582394,

  title        = {Density-functional study of the La2Zr2O7 low-index surfaces},

  author       = {Mantz, Yves A. and Duan, Yuhua},

  abstractNote = {We report that in order to explain the ability of lanthanum zirconate (La2Zr2O7, LZ) and various doped forms of LZ to function as catalysts, an understanding of LZ surface structures is needed. Accordingly, certain LZ surfaces that are expected to be prevalent in prepared samples of LZ, namely, the low-index (001), (011), and (111) surfaces, are examined at the level of density-functional theory. All possible surface terminations of these surfaces formed by cleaving a perfect LZ crystal, termed ideal surface terminations, are considered, as well as several defective surface terminations of a given surface. Surface energies and surface free energies are computed, and surface phase diagrams (SPDs) of the (001), (011), and (111) surfaces are obtained. From these SPDs, the thermodynamically preferred surface termination of the (001), (011), or (111) surface is concluded to be nonideal over a large range of temperature and oxygen gas partial pressure conditions. This finding is unchanged if the SPDs are determined more accurately by taking into account certain vibrational contributions obtained from computed phonon dispersions. Additionally, a way to use results to characterize the surfaces of synthesized LZ crystallites is discussed, but the shapes or dimensions of the crystallites first need to be obtained.},

  doi          = {10.1016/j.susc.2018.04.010},

  journal      = {Surface Science},

  number       = C,

  volume       = 689,

  place        = {United States},

  year         = {2018},

  month        = {4}

}

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Title: Density-functional study of the La2Zr2O7 low-index surfaces

Abstract

Citation Formats

Title: Density-functional study of the La₂Zr₂O₇ low-index surfaces