A method was presented for computing the electrical impedance of solid oxide electrolyte from kinetic Monte Carlo simulations of oxygen vacancy diffusion. The impedance values at all frequencies were obtained from a single equilibrium simulation based on the fluctuation-dissipation theorem, leading to a significant gain of efficiency over existing methods. This permitted the systematic examination of the effect of dopant concentration. Increasing dopant concentration was found to decrease the infinite-frequency impedance, which was attributed to the increasing density of oxygen vacancies. The difference between the impedance values at zero- and infinite-frequency, on the other hand, showed the opposite trend, and was linked to dopant-vacancy interactions. Hence the two competing mechanisms, previously proposed to explain the existence of an optimal doping concentration, were separately quantified. This model also predicted a significant effect of the arrangement of dopant cations upon the electrolyte conductivity.

Kinetic Monte Carlo Simulations of Oxygen Vacancy Diffusion in a Solid Electrolyte: Computing the Electrical Impedance using the Fluctuation-Dissipation Theorem. E.Lee, F.B.Prinz, W.Cai: Electrochemistry Communications, 2010, 12[2], 223-6