Stability of FeVO4 under Pressure: An X-ray Diffraction and First-Principles Study

The high-pressure behavior of the crystalline structure FeVO4 has been studied by means of X-ray diffraction using a diamond-anvil cell and first-principles calculations. The experiments were carried out up to a pressure of 12.3 GPa, until now the highest pressure reached to study an FeVO4 compound. High-pressure X-ray diffraction measurements show that the triclinic P1 (FeVO4-I) phase remains stable up to ≈3 GPa; then a first-order phase transition to a new monoclinic polymorph of FeVO4 (FeVO4-II′) with space group C2/m is observed, having an α-MnMoO4-type structure. A second first-order phase transition is observed around 5 GPa toward the monoclinic (P2/c) wolframite-type FeVO4-IV structure, which is stable up to 12.3 GPa in coexistence with FeVO4-II′. The unit cell volume reductions for the first and second phase transitions are ΔV = −8.5% and −13.1%. It was observed that phase transitions are irreversible and both high-pressure phases remain stable once the pressure is released. Calculations were per...