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

Abstract

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.Surface 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<1200K for X≥0.05. For a system with X=0.01 anion migration energies of 0.82eV and 0.77eV, and anti-Frenkel pair formation energies of 3.01eV and 4.04eV on the surface and in the bulk, respectively, were obtained.