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

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Understanding the high-pressure behavior of transition metal oxides is crucial for materials science.
• Iron vanadium oxide (FeVO4) is a compound with potential applications, but its high-pressure structural phases are not fully characterized.

Purpose of the Study:

• To investigate the high-pressure structural phase transitions of FeVO4 using experimental and theoretical methods.
• To determine the stability of different FeVO4 polymorphs under extreme pressure conditions.

Main Methods:

• High-pressure X-ray diffraction (XRD) using a diamond-anvil cell up to 12.3 GPa.
• First-principles calculations employing generalized gradient approximation plus Hubbard correction (GGA+U) and hybrid Heyd-Scuseria-Ernzerhof (HSE06) functionals.

Main Results:

• FeVO4 exhibits two first-order phase transitions: triclinic P1̅ (FeVO4-I) to monoclinic C2/m (FeVO4-II') around 3 GPa, and then to monoclinic P2/c (FeVO4-IV) around 5 GPa.
• Significant volume reductions of -8.5% and -13.1% were observed during these transitions.
• The high-pressure phases (FeVO4-II' and FeVO4-IV) are irreversible and remain stable upon pressure release.
• Theoretical calculations show good agreement with experimental data for structural parameters.
• Predicted further transitions to raspite-type (FeVO4-V) and AgMnO4-type (FeVO4-VI) structures at 36 GPa and 66.5 GPa, respectively.

Conclusions:

• FeVO4 undergoes complex, irreversible phase transitions under high pressure, leading to novel structural phases.
• The study provides a comprehensive understanding of FeVO4's pressure-induced structural evolution, supported by robust theoretical validation.
• The findings contribute to the knowledge of high-pressure behavior in vanadate compounds and suggest potential for new material phases at extreme conditions.