Structural evolution of the CuGaO2 delafossite under high pressure

We have performed pseudopotential calculations and x-ray-diffraction and x-ray-absorption measurements on the CuGaO2 delafossite under high pressure. We have completely characterized the structural behavior of the low pressure phase. We have found out that the a axis is more compressible than the c axis, and as a consequence the oxygen octahedra defined by the gallium environment tend to become more regular under high pressure. We have determined the internal parameter describing the oxygen position inside the unit cell, and seen that it is nearly constant when pressure is applied. We have observed an irreversible phase transition affecting the copper environment but not the gallium one. Such phase transition begins at 24+/-2 GPa and is completed at 28+/-2 GPa.