Thermodiffusion and ion transport in doped ceria by molecular dynamics simulations

We simulated thermodiffusion and ionic conductivity in doped ceria by molecular dynamics. Four approaches to estimate the ionic conductivity were applied using the auto-correlation function and collective displacement of oxygen ions, the tracer diffusion coefficient from the mean squared displacement, and the displacement in an electric field. The Green-Kubo method was applied to determine the mass-heat coupling cross-coefficients L-0q and L-q0 of the Onsager transport matrix. This is the first calculation of these coefficients in an ionic compound. The simulated parameters are negative throughout the applied temperature range suggesting net transport of anions from a cold to a hot region in a temperature gradient. The results emphasize that the coupling between mass and heat transport in an oxygen ion electrolyte could have an impact for practical applications. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.