Structures of Defect Clusters on Ceria {111} Surface

Defect clusters containing oxygen vacancies and Ce3+ cations on ceria (CeO2) surface dominate the
electronic
and chemical properties of the surface. However, the structures of
the clusters, especially the arrangements of the oxygen vacancies
in the clusters, have not been explained consistently. In this work,
atomistic simulation based on energy minimization has been used to
investigate the cluster structures on ceria {111} surface. It was
found out that the oxygen vacancies are energetically favorable to
be at the second-neighbor sites to their associated Ce3+ cations. Moreover, the subsurface oxygen vacancies on the third
layer are essential for the arrangement of the surface oxygen vacancy
clusters. Due to the existence of the subsurface oxygen vacancies,
the adjacent surface oxygen vacancies tend to be separated by ⟨110⟩/2,
and the linear surface clusters are more energetically favorable than
the triangle ones. Then, the structure development with cluster size
is discussed.