The crucial role of defect interactions for thermodynamics and kinetics in solid state Ionics

Defect interactions play a crucial role for thermodynamics and kinetics in Solid State Ionics. They strongly affect both the thermodynamics of defect formation in a solid and the mobility of defects and ions. This applies in particular to oxides with relatively high defect concentrations, which are nowadays used in many technical applications such as sensors, electrolyzers, solid oxide fuel cells etc. As examples for this class of oxides we consider ceria as prototype mixed ionic-electronic conductor, doped ceria as prototype oxygen ion conductor, and doped barium zirconate as prototype proton conductor. Here we summarize our years of computational work in which we applied density functional theory (DFT) in combination with Metropolis Monte Carlo simulations (MMC) and kinetic Monte Carlo simulations (KMC) to investigate the defect chemistry and ion transport in these prototype oxides.