Structural dynamics of Schottky and Frenkel defects in CeO₂: a density-functional theory study

Abstract

Cerium dioxide CeO2 (ceria) is an important material in catalysis and energy applications. The intrinsic Frenkel and Schottky defects can impact a wide range of material properties including the oxygen storage capacity, the redox cycle, and the ionic and thermal transport. Here, we study the impact of Frenkel and Schottky defects on the structural dynamics and thermal properties of ceria using density functional theory. The phonon contributions to the free energy are found to reduce the defect formation free energies at elevated temperature. The phonon dispersions of defective CeO2 show significant broadening of the main branches compared to stoichiometric ceria. Phonon modes associated with the defects are identifiable in the infrared spectra through characteristic shoulders on the main features of the stoichiometric fluorite structure. Finally, the presence of Frenkel and Schottky defects are also found to reduce the thermal conductivity by up to 88% compared to stoichiometric CeO2.

Analysis of defects dominating carrier recombination in CeO2 single crystal for photocatalytic applications

“…In recent reports about defects in CeO 2 , Smith's group investigate the identification and quantification of Frenkel and Schottky defects through infrared spectra, the effect of phonon-free energy on defect formation energies, and the estimation of the impact of defects on thermal conductivity using density functional theory (DFT) [17]. Zhang's group focuses on the development and validation of novel interatomic potentials and methodologies to accurately predict defect chemistry in CeO 2 using experimental measurements and DFT calculations [18].…”