Possible orthorhombic phase of Ta₂O₅ under high pressures

A potential orthorhombic phase of Ta₂O₅, designated as Y-Ta₂O₅, is predicted under high-pressure conditions using density functional theory (DFT) combined with structural search algorithms. This phase, containing four formula units per unit cell (Z = 4), exhibits the highest Ta–O coordination numbers reported to date. Y-Ta₂O₅ is identified as the most energetically stable form of Ta₂O₅ within the pressure range of approximately 70 GPa to at least 200 GPa. Both standard DFT-GGA and higher-accuracy GW calculations indicate that Y-Ta₂O₅ is a wide-bandgap semiconductor with a direct bandgap. Furthermore, nuclear quantum effects (NQEs) introduce nontrivial corrections to external pressure at fixed volumes, underscoring their significance in high-pressure phase stability analyses.