Charge States of Ions around Σ5(310)/[001] Grain Boundary in Cubic-ZrO<sub>2</sub> Revealed by First-principles Calculations

Understanding ion behavior is crucial for advancing the processing of ceramic materials. Given that ion transport predominantly occurs at grain boundaries (GBs) in ceramics, investigating the electronic states in their vicinity is essential. In this study, we perform electronic structure and Born effective charge (BEC) calculations from first principles based on density functional (perturbation) theory, focusing specifically on the Σ5(310)/[001] GB in cubic-ZrO2. Our results reveal the emergence of acceptor states just above the top of the valence band near the GB region. Furthermore, we observe significant deviations in the BECs of both Zr and O near the GB region compared to those in the bulk. These findings suggest the possibility of peculiar ion behavior near GB regions, particularly under applied electric fields.