Comment on “Atomic-scale model of the grain boundary potential in perovskite oxides”

We discuss the recent proposal by Klie et al. [Phys. Rev. B 68, 214101 (2003)] that a Thomas-Fermi screening model provides a better description of grain-boundary potentials in acceptor-doped $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ than the established double-Schottky-barrier model. We point out several inconsistencies between the model predictions and experimental observations.