Exploring the thermodynamic stability and electronic structure of ZnNb₂O₆(001) surface through first-principles calculations

The polar surface of ZnNb₂O₆ material holds considerable importance and practical significance. Using first-principles calculations, the structure, charge redistribution, electronic properties, and thermodynamic stability of the ZnNb₂O₆(001) surface were examined. The crystal was cleaved along the (001) plane to form nine surface slab models, of which five surface terminations are feasible under specific chemical conditions. The optimized structural configurations of these terminations illustrate the charge transfer due to polarity compensation and the differences in electronic structure caused by surface reconstruction. Surface metallization, resulting from the atypical saturation of surface states, acts as a compensatory mechanism for pronounced surface polarity. The ZnNb₂O₆(001) surface slab exhibits a shift in its electronic band structure, transitioning from semiconductor characteristics to metallic properties. The nature of the charge carriers (p-type or n-type) depends on the specific surface termination. The unique electronic properties of the ZnNb₂O₆(001) surface arise from significant variations in volume and polarity compensation. This detailed atomic-level understanding is expected to stimulate further theoretical and experimental investigations into this novel photocatalytic material.