Anisotropic compression in the high-pressure regime of pure and chromium-doped vanadium dioxide

We present structural studies of V1-xCrxO2 (pure, 0.7 %, and 2.5% Cr-doped) compounds at room temperature in a diamond anvil cell for pressures up to 20 GPa using synchrotron x-ray powder diffraction. All the samples studied show a persistence of the monoclinic M-1 symmetry between 4 and 12 GPa. Above 12 GPa, the monoclinic M-1 symmetry changes to isostructural M-x phase (space group P2(1)/c) with a significant anisotropy in lattice compression of the b-c plane of the M-1 phase. This behavior can be reconciled invoking the pressure-induced charge delocalization.