Molecular dynamics simulation on ionic conduction process of oxygen in Ce_(1-x)M_xO_(2-x/2)

摘要

Molecular dynamics simulation of CeO_2 doped with M~(3+) (a trivalent cation) with ionic radii ranging from 1.019 A (Y~(3+)) to 1.160 A (La~(3+)) were performed to examine the effects of the dopant cation size on ionic conductivity. Interatomic potential parameters were empirically fitted with equilibrium properties and energy barriers from ab initio calculations. Vacancy trapping and edge blocking mechanisms were studied. Analysis on vacancy trapping showed that the effect was more pronounced in La- and Y-doped ceria than those doped with Gd and Sm. Analysis of the edge blocking effect showed that larger-sized dopants would limit the available pathways for vacancy hopping. The combined effects satisfactorily explained the influence of the dopant cation size on the ionic conductivity of heavily doped ceria.