研究目的
To rigorously determine the physical oxidation state of Ce in ceria-based materials through first-principles DFT + U calculations, understanding its dependence on local structure and chemical surroundings, and its implications for material design and applications.
研究成果
The study successfully determines the physical oxidation states of Ce in various ceria-based materials, showing that Ce oxidation state is influenced by local structure and chemical environment. Oxygen vacancies facilitate the reduction of Ce4+ to Ce3+, and the presence of Ti and V can also affect Ce oxidation states, especially under oxygen-deficient conditions. These findings provide a foundation for understanding and designing ceria-based materials with tailored properties for specific applications.
研究不足
The study focuses on bulk materials and may not fully capture surface or interface effects. The computational models assume certain crystal structures and may not account for all possible configurations or defects in real materials.
1：Experimental Design and Method Selection:
First-principles DFT + U calculations were performed using the Vienna Ab initio Simulation Package (VASP) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and projector augmented wave (PAW) pseudopotentials. The Hubbard model was used to treat strong correlations of 4f (Ce) and 3d (Ti and V) electrons.
2：Sample Selection and Data Sources:
Selected ceria-based materials include binary oxides (CenO2n-2, n = 7, 9, 10, 11, 12), ternary (Ce-Ti(V)-O), and quaternary (Ce-Ti-V-O) compounds.
3：List of Experimental Equipment and Materials:
Computational simulations were conducted using VASP software with a plane-wave kinetic energy cutoff of 500 eV.
4：Experimental Procedures and Operational Workflow:
Convergence was reached when total energies converged within 1 × 10?5 eV and Hellmann-Feynman forces on each ion were less than
5：02 eV/?. The tetrahedron method with Bl?chl correction was used for Brillouin-zone integration. Data Analysis Methods:
Occupation numbers of 4f orbitals were calculated to determine the physical oxidation state (OSp) of Ce ions. Bader charge analysis was also performed to understand charge transfer.
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