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Ab initio thermodynamics of intrinsic oxygen vacancies in ceria

Gopal, Chirranjeevi Balaji and van de Walle, Axel (2012) Ab initio thermodynamics of intrinsic oxygen vacancies in ceria. Physical Review B, 86 (13). Art. No. 134117. ISSN 1098-0121. doi:10.1103/PhysRevB.86.134117.

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Nonstoichiometric ceria(CeO_(2−δ)) is a candidate reaction medium to facilitate two-step water splitting cycles and generate hydrogen. Improving upon its thermodynamic suitability through doping requires an understanding of its vacancy thermodynamics. Using density functional theory (DFT) calculations and cluster expansion-based Monte Carlo simulations, we have studied the high-temperature thermodynamics of intrinsic oxygen vacancies in ceria. The DFT+U approach was used to get the ground state energies of various vacancy configurations in ceria, which were subsequently fit to a cluster expansion Hamiltonian to efficiently model the configurational dependence of energy. The effect of lattice vibrations was incorporated through a temperature-dependent cluster expansion. Lattice Monte Carlo simulations using the cluster expansion Hamiltonian were able to detect the miscibility gap in the phase diagram of ceria. The inclusion of vibrational and electronic entropy effects made the agreement with experiments quantitative. The deviation from an ideal solution model was quantified by calculating as a function of nonstoichiometry, (a) the solid state entropy from Monte Carlo simulations, and (b) Warren-Cowley short range order parameters of various pair clusters.

Item Type:Article
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van de Walle, Axel0000-0002-3415-1494
Additional Information:© 2012 American Physical Society. Received 20 June 2012; revised manuscript received 11 September 2012; published 23 October 2012. Work was supported by the National Science Foundation under CAREER Grant DMR-1154895 and by Teragrid/ XSEDE computational resources provided by NCSA and TACC under Grant No. DMR050013N.
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National Center for Supercomputing Applications (NCSA)DMR050013N
Issue or Number:13
Classification Code:PACS: 61.72.Bb, 81.30.Bx,, 88.05.De
Record Number:CaltechAUTHORS:20121126-091706673
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35619
Deposited By: Tony Diaz
Deposited On:26 Nov 2012 22:20
Last Modified:09 Nov 2021 23:16

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