Figure 5.

Equation of state and pressure-response of crystal lattice parameters in β- and γ-Cu₂V₂O₇ to 4 GPa. (a) Normalized unit cell volume as a function of increasing pressure up to 4 GPa. (b) Normalized stress as a function of Eulerian strain for the experimental data. (c) Lattice constants a, b, and c, and (d) unit cell angles, α, β, and γ, as functions of pressure. Data corresponding to β-Cu₂V₂O₇ (γ-Cu₂V₂O₇) are shown in black (blue). (a, c, d) Solid (dashed) lines correspond to second-order Birch–Murnaghan equations of state (BM EoS) fitted to the experimental (calculated) data. Vertical dashed gray lines show the approximate phase transition pressure. The labels “ULL” and “ALBA” respectively signify data collected in-house at the University of La Laguna and at ALBA Synchrotron. ICSD refers to the ambient condition (atmospheric pressure and room temperature) γ-Cu₂V₂O₇ structure of ref (9) taken from the Inorganic Crystal Structure Database.