Columbite Single-Crystal CoV₂O₆ under High Pressure: An XRD and Raman Spectroscopy Study

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Orthorhombic columbite CoV₂O₆ is a material with potential applications.
• Understanding its behavior under extreme conditions is crucial for materials science.

Purpose of the Study:

• To investigate the structural and vibrational properties of orthorhombic columbite CoV₂O₆ under high pressure.
• To identify and characterize phase transitions induced by pressure.

Main Methods:

• Single-crystal X-ray diffraction (XRD) up to 54.9 GPa.
• Raman spectroscopy up to 54.9 GPa.
• Density functional theory (DFT) calculations.

Main Results:

• Two reversible phase transitions were observed at 20.0 GPa and 45.6 GPa.
• The first transition (20.0 GPa) is isostructural with a 4.7% volume reduction and symmetrization of VO₆ octahedra.
• A new monoclinic polymorph (space group P2₁/c) was identified above 45.6 GPa.
• Below 4.9 GPa, the material transforms into the brannerite polymorph.

Conclusions:

• High pressure significantly alters the structure of CoV₂O₆, leading to distinct polymorphs.
• The observed transitions are reversible, with complex behavior upon pressure release.
• Experimental findings are consistent with theoretical DFT calculations.