Strain-Induced Phase and Oxygen-Vacancy Stability in Ionic Interfaces from First-Principles Calculations

Understanding interfacial chemistry is becoming crucial in materials design for heterointerfaces. Using density functional theory, we elucidate the effect of strained interfaces on phase and oxygen-vacancy stability for CeO2 vertical bar ZrO2, ThO2 vertical bar ZrO2 and CeO2 vertical bar ThO2 interfaces. The calculations show that ZrO2 transforms from cubic fluorite to the orthorhombic columbite under tensile strain providing evidence of a previous experimental speculation of an unrecognized ZrO2 phase. We also show oxygen vacancy formation energy decreases in the presence of tensile strain. As a result, the interfacial strain could be used as a knob to stabilize oxygen vacancies on either side of the interface, and control their concentration for fast-ion conductor applications.