Understanding Ceria Nanoparticles from First-Principles Calculations

High Resolution Image Download MS PowerPoint Slide Octahedral clusters (CeO 2 - x ) n ( n ≤ 85) have been studied using a density functional method (DFT+U) adapted to model nanocrystalline ceria. The binding energies of the clusters Ce 19 O 32, Ce 44 O 80, and Ce 85 O 160 are shown to converge to the bulk limit almost linearly with respect to the average coordination number of Ce. The experimentally detected anomalous lattice expansion for nanoscale (CeO 2 - x ) n particles of decreasing size is explicitly assigned to the presence of oxygen vacancies. Partially reduced Ce 3+ cations are found to occupy more open edge and corner sites of the nanoparticles, whereas most oxidized Ce 4+ centers are located in highly coordinated positions. This finding is crucial for the understanding of ceria reactivity at the nanoscale.