Structure and mass transport characteristics of the surface of gadolinium-doped ceria nanocrystals: Molecular dynamics study

Surface of CGO nanocrystals in a vacuum was investigated by MD method in a wide temperature range with five different potentials. Temperature dependences of distances between cations in near-surface layers in the direction along the surface and to the nanocrystal center were studied in detail. Surface area ratio S(100)/S(111) for equilibrium shape of truncated octahedron has maximum for nanocrystals of 6000–12,000 ions. e ion displacement was decomposed on the path along the surface and into the bulk of nanocrystal. The diffusion of surface ions in the entire temperature range has predominantly two-dimensional character, regardless of potentials and the dopant concentration X. Anion diffusion coefficients on the surface and in the bulk were compared, they coincide at T < 1200 K for X ≥ 0.05. For a system with X = 0.01 anion migration energies of 0.82 eV and 0.77 eV, and anti-Frenkel pair formation energies of 3.01 eV and 4.04 eV on the surface and in the bulk, respectively, were obtained.