Pressure-induced phase transition in transition metal trifluorides

As a fundamental thermodynamic variable, pressure can alter the bonding patterns and drive phase transitions leading to the creation of new high-pressure phases with exotic properties that are inaccessible at ambient pressure. Using the swarm intelligence structural prediction method, the phase transition of TiF3, from R–3c to the Pnma phase, was predicted at high pressure, accompanied by the destruction of TiF6 octahedra and formation of TiF8 square antiprismatic units. The Pnma phase of TiF3, formed using the laser-heated diamond-anvil-cell technique was confirmed via high-pressure x-ray diffraction experiments. Furthermore, the in situ electrical measurements indicate that the newly found Pnma phase has a semiconducting character, which is also consistent with the electronic band structure calculations. Finally, it was shown that this pressure-induced phase transition is a general phenomenon in ScF3, VF3, CrF3, and MnF3, offering valuable insights into the high-pressure phases of transition metal trifluorides.