Entropies of defect association in ceria from first principles.

Defects and their interactions play a crucial role for the properties of solid state materials. While energies of defect formation and defect interaction are commonly calculated from first principles, calculations of corresponding vibrational entropies in solids are less common due to the high computational demand. This is in particular true for defect pairs as the existence of multiple defects lowers the symmetry of the cell. Here, we determine the entropies of association of defects in doped cerium oxide by density functional theory and phonon calculations. We estimate the importance of the entropic contribution in the constant volume and constant pressure case and address the limitations of the calculations. The small values of the calculated entropies render the accurate determination difficult. However, even small entropy contributions could have a significant influence on defect interactions and ordering at high temperature.