Influence of impurity-vacancy disorder on characteristics of gadolinium-doped ceria oxide: Molecular dynamics study

By high-speed MD method using GPU the CGO nanocrystals of about 40,000 particles during about 0.1μs, in the temperature range (2500–700) K, were simulated. The influence of different dopant distributions on the nanocrystal characteristics, for two potentials sets, was investigated. For a given potentials set Gd distribution does not affect the lattice parameter and the anion diffusion coefficients. Five types of impurity vacancies were defined, by the Gd number in the nearest neighborhood, and temperature dependences were built. The formation energies of vacancies of all types were obtained. Calculated by the MD conductivity activation energy of 0.6eV acceptable coincides with the experimental 0.7eV, just as the absolute conductivity values. The supposition that helium in CGO ceramics dissolve in vacancies, surrounded only by cerium ions, was discussed. Analysis of the MD, conductivity measurements and helium defectoscopy shows that up to the melting temperature the vacancies are mainly associated with impurity ions.