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Thermally activated defect tolerance of the oxygen vacancies in CeO2 revealed by machine-learning molecular dynamics
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DOI：10.1039/D6CP00774K.png)
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Abstract
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Thermal instability and uncontrolled defect dynamics continue to be major obstacles to the reliable functioning of oxide-based energy materials under practical operating conditions. Due to its propensity for reversibly producing oxygen vacancies; cerium dioxide (CeO2) is widely used in energy-related applications; nevertheless; the finite-temperature stability mechanisms leading to vacancy tolerance are still poorly understood. In this work; machine-learning molecular dynamics has been applied to thoroughly examine the dynamical and thermodynamic stability of oxygen vacancies in bulk CeO2 at device-relevant temperatures (300–500 K). By directly linking vacancy formation energetics with finite-temperature lattice dynamics; a quantitative vacancy stability paradigm that encompasses both dynamic resilience and energetic accessibility has been presented. According to our findings; the oxygen vacancies in CeO2 dynamically accommodate lattice distortions and intrinsically modest formation energies; which allow thermal disorders without long-range structural deterioration. Even at high temperatures; the root-mean-square displacement; mean-square displacement; and radial distribution analyses show reduced defect-driven diffusion and maintained crystallinity. We create a hierarchical vacancy stability phase map that outlines a wide defect-tolerant operating window for CeO2 by integrating these descriptors. These findings establish the physical origin of defect tolerance in ceria and provide a material-level framework for the rational design and thermal optimization of defect-engineered oxide energy materials.
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