Atomistic simulation based on energy minimization techniques was carried out to study the association energies of more than 300 defect structures of ceria doped with Lu2O3, Yb2O3, Er2O3, Y2O3, Gd2O3, Eu2O3, Sm2O3, Nd2O3 and La2O3. The calculation ensemble includes all the possible defect structures in 6.25 mol% doped ceria. It is revealed that a clear preference for vacancy-dopant association occurs energetically for small dopant cations and vacancy-Ce4+ association for large dopant cations, with the crossover at Gd3+. The defect structures with the maximum association effect for different trivalent cations were determined. For Gd3+ doped ceria which presents the lowest association effect in the trivalent doped ceria, the association energies of four different defect structures are extremely close, which agrees well with a recent EXAFS investigation, that is, Gd3+ is distributed randomly in the ceria lattice. This work provides insight for the understanding of ionic conductivity in doped ceria. (C) 2008 Elsevier B.V. All rights reserved.