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 monoclinicM1 symmetry between 4 and 12 GPa. Above 12 GPa, the monoclinic M1 symmetry changes to isostructural Mx phase (space group P21/c) with a significant anisotropy in lattice compression of the b-c plane of the M1 phase. This behavior can be reconciled invoking the pressure-induced charge delocalization