High-Pressure Phase Diagram of the Ti–O System

Titanium oxides are technologically important compounds. The chemistry of the Ti–O system is quite rich, largely because of the multiple oxidation states that titanium atoms can take. In this work, using a combination of variable-composition evolutionary crystal structure prediction (USPEX code) and data mining (Materials Project), we predicted all of the stable titanium oxides in the pressure range 0–200 GPa and found that 27 compounds can be stable at different pressures. We resolved contradictions between previous works and predicted four hitherto-unknown stable phases: P 2 1 / c -TiO 3, I 4/ mmm -Ti 3 O 2, Imm 2-Ti 5 O 2, and R 3̅-Ti 12 O 5 . We also showed that the high-pressure P 6̅ m 2-TiO phase is an electride.