Prediction of Fe2P -type TiTe2 under pressure

$\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type dioxides are significant both for geoscience and condensed-matter physics. For example, $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type $\mathrm{Si}{\mathrm{O}}₂$ has been proposed to be one of the dominant components in the mantles of super-Earths and $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type $\mathrm{Ti}{\mathrm{O}}₂$ has been shown to have a large visible absorbance. Here we report the discovery of an $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type phase in a typical transition-metal dichalcogenide (TMD), $\mathrm{TiT}{\mathrm{e}}₂$, using crystal structure prediction and first-principles calculations. Ambient layered $\mathrm{TiT}{\mathrm{e}}₂$ will first transform to a monoclinic $C2/m$ phase and then finally to the hexagonal $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type phase above 33 GPa. $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type $\mathrm{TiT}{\mathrm{e}}₂$ is predicted to be metallic, contrasting with the semiconductivity of $\mathrm{F}{\mathrm{e}}₂\mathrm{P}$-type $\mathrm{Ti}{\mathrm{O}}₂$. The same high-pressure phase ($\mathrm{F}{\mathrm{e}}₂\mathrm{P}$ type) appears both in transition-metal dioxides and TMDs, indicating that the stacking patterns of anions and cations play an increasingly important role in determining the high-pressure phase.