PbV₂O₆ under compression: near zero-linear compressibility and pressure-induced change in vanadium coordination

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Understanding the behavior of inorganic compounds under extreme pressure is crucial for materials science.
• Lead metavanadate (PbV2O6) is an inorganic compound whose high-pressure properties are not fully understood.
• Zero-linear compressibility is a rare phenomenon with potential applications in material design.

Purpose of the Study:

• To investigate the structural and vibrational evolution of lead metavanadate (PbV2O6) under high pressure.
• To determine if PbV2O6 exhibits zero-linear compressibility and understand the underlying mechanisms.
• To characterize the phase stability and electronic properties of PbV2O6 up to 20 GPa.

Main Methods:

• Synchrotron powder X-ray diffraction was used to monitor structural changes under pressure.
• Raman spectroscopy identified vibrational modes and their pressure dependencies.
• Density-functional theory (DFT) simulations provided theoretical support for experimental observations.

Main Results:

• PbV2O6 demonstrated zero-linear compressibility, maintaining its crystal size along one axis up to 20 GPa.
• No structural phase transitions were observed, but vanadium coordination polyhedra transformed progressively.
• A bulk modulus of 86.1(9) GPa was determined, and the band gap was found to close with increasing pressure.

Conclusions:

• Lead metavanadate (PbV2O6) is a novel material exhibiting zero-linear compressibility due to vanadium coordination changes.
• The material remains structurally stable up to 20 GPa, with anisotropic compressibility.
• The pressure-induced band gap closure is attributed to the Pb 6s orbital's contribution to the valence band.