Journal article

Publication year: 2020

Pages: 15831-15838

Journal: Journal of Physical Chemistry C

Volume number: 124

Issue number: 29

ISSN: 1932-7447

DOI Link: https://doi.org/10.1021/acs.jpcc.0c05352

Publisher: American Chemical Society

Abstract: 
Ce1-xPrxO1-delta (CPO) is a prominent mixed ionic and electronic conductor known for its unique oxygen storage capacity due to two redox-active cations. The oxygen storage properties depend on both the redox behavior and mobility of ions and electrons. The electronic properties of CPO are defined by the f-states of the two lanthanides and described within the model of small polarons. The theoretical treatment of small polarons is already challenging; additionally, the description of heavier elements, such as the lower transition metals and lanthanides, typically involves relativistic effects, such as spin-orbit coupling (SOC). These affect the electronic properties of materials and, therefore, also the thermodynamic parameters, such as phase stability and redox potential. Up to now, the f-electrons of Pr-ions and the corresponding redox chemistry have not been treated computationally, and their contribution to the mixed conduction and oxygen storage capacity in CPO has been neglected. Here, we investigate both the stoichiometric and defective CPO with respect to the localized electrons in the Pr(4f)-states. Density functional theory plus Hubbard U calculations were performed with and without the implementation of SOC. Only when accounting for relativistic interactions in the calculations, CPO shows semiconducting behavior with polaronic intragap states, in agreement with experimental findings, while otherwise, a metal-like behavior with degenerated f-states right at the Fermi level is found. Our results distinctly reveal the importance of spin-orbit interactions for a correct theoretical description of polarons in f-states. The electronic structure of CPO is revised, that is, the energetic and geometric overlap of states and, therefore, the bonding interactions within the crystal.

Harvard Citation style: Michel, K., Bjørheim, T., Norby, T., Janek, J. and Elm, M. (2020) Importance of the Spin-Orbit Interaction for a Consistent Theoretical Description of Small Polarons in Pr-Doped CeO2, Journal of Physical Chemistry C, 124(29), pp. 15831-15838. https://doi.org/10.1021/acs.jpcc.0c05352

APA Citation style: Michel, K., Bjørheim, T., Norby, T., Janek, J., & Elm, M. (2020). Importance of the Spin-Orbit Interaction for a Consistent Theoretical Description of Small Polarons in Pr-Doped CeO2. Journal of Physical Chemistry C. 124(29), 15831-15838. https://doi.org/10.1021/acs.jpcc.0c05352