Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria

Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria.

We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO(2) (ceria) as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+U and GGA+U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Se...

Ab-initio thermodynamics of intrinsic oxygen vacancies in ceria

Nonstoichiometric ceria(CeO2−δ) is a candidate reaction medium to facilitate two step water splitting cycles and generate hydrogen. Improving upon its thermodynamic suitability through doping requires an understanding of its vacancy thermodynamics. Using density functional theory(DFT) calculations and a cluster expansion based Monte Carlo simulations, we have studied the high temperature thermo...

Oxygen Vacancies at Grain Boundaries in Doubly-Doped Ceria Determined using EELS

In oxygen conducting ceramics such as cerium-based oxides, O 2diffusion occurs via vacancy hopping. The vacancy concentration can be modulated through doping with aliovalent cations such as Gd 3+ or Pr 3+ . Sluggish ionic conductivity in these electrolytes has been attributed to various defects which increase the activation energy for anion migration. The association of mobile oxygen vacancies ...

Volume-dependent electron localization in ceria

Density-functional calculations of the structure of near-surface oxygen vacancies and electron localization on CeO2(111).

One of the most topical issues surrounding oxygen vacancies on CeO2(111) is the relative stability of surface and subsurface defects. Using density-functional theory (DFT) with the HSE06 (Heyd-Scuseria-Ernzerhof) hybrid functional as well as the DFT+U approach (where U is a Hubbard-like term describing the on-site Coulomb interactions), we find subsurface vacancies with (2x2) periodicity to be ...