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Issue 45, 2016
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Unravelling the fundamentals of thermal and chemical expansion of BaCeO3 from first principles phonon calculations

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Abstract

Differentiating chemical and thermal expansion is virtually impossible to achieve experimentally. While thermal expansion stems from a softening of the phonon spectra, chemical expansion depends on the chemical composition of the material. In the present contribution, we, for the first time, completely decouple thermal and chemical expansion through first principles phonon calculations on BaCeO3, providing new fundamental insights to lattice expansion. We assess the influence of defects on thermal expansion, and how this in turn affects the interpretation of chemical expansion and defect thermodynamics. The calculations reveal that the linear thermal expansion coefficient is lowered by the introduction of oxygen vacancies being 10.6 × 10−6 K−1 at 300 K relative to 12.2 × 10−6 K−1 for both the protonated and defect-free bulk lattice. We further demonstrate that the chemical expansion coefficient upon hydration varies with temperature, ranging from 0.070 to 0.115 per mole oxygen vacancy. Ultimately, we find that, due to differences in the thermal expansion coefficients under dry and wet conditions, the chemical expansion coefficients determined experimentally are grossly underestimated – around 55% lower in the case of 10 mol% acceptor doped BaCeO3. Lastly, we evaluate the effect of these volume changes on the vibrational thermodynamics.

Graphical abstract: Unravelling the fundamentals of thermal and chemical expansion of BaCeO3 from first principles phonon calculations

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Publication details

The article was received on 17 Aug 2016, accepted on 19 Oct 2016 and first published on 19 Oct 2016


Article type: Paper
DOI: 10.1039/C6CP05710A
Citation: Phys. Chem. Chem. Phys., 2016,18, 31296-31303
  • Open access: Creative Commons BY-NC license
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    Unravelling the fundamentals of thermal and chemical expansion of BaCeO3 from first principles phonon calculations

    A. Løken, R. Haugsrud and T. S. Bjørheim, Phys. Chem. Chem. Phys., 2016, 18, 31296
    DOI: 10.1039/C6CP05710A

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