Atomic and Electronic Structure of Cerium Oxide Stepped Model Surfaces

The atomic and electronic structure of ceria surfaces exhibiting step edges have been studied by means of periodic density functional (LDA+U and GGA+U) calculations. A variety of stoichiometric and nonstoichiometric models of increasing complexity have been designed. The electronic structure has been explored using the topological Bader analysis, the calculated magnetic moments and the ELF (electron localization function) maps. It is concluded that Ce3+ atoms may exist even in stoichiometric extended ceria samples and that the presence of oxygen vacancies in stepped surfaces also induces the presence of Ce3+ atoms although in both cases, the reduced atoms tend to occupy the sites with smallest possible coordination number.