Hydration properties of BaSn0.875M0.125O3-δ substituted by large dopants (M= In, Y, Gd, and Sm) from first

The hydration properties of barium stannate doped by trivalent elements (12.5%) are investigated by using density-functional calculations. The interaction energies of defects are computed in different relative positions, revealing that at this high doping level, similar to that currently used in experiments, the first-neighbor positions (between dopants and protons and between dopants and oxygen vacancies) are not always the most stable ones. The reasons for this unexpected energy landscape are analyzed in terms of structural distortions around dopants and dopant-proton and/or dopant-vacancy interaction overlaps. It is attributed to the large size of the dopants considered compared to that of Sn.