X-ray diffraction study of the icosahedral AlCuFe quasicrystal at megabar pressures

We report in-situ synchrotron X-ray diffraction study of icosahedral (i)-AlCuFe quasicrystal (QC) at high pressure up to 104 GPa under ambient temperature using the diamond anvil technique. With compression, there is no obvious change of the diffraction pattern within the measured pressure range. Five characteristic peaks from the i-AlCuFe QC maintain up to 104 GPa. The unit cell volume of the i-AlCuFe QC decreases monotonously until 72 GPa. The experimental P-V compression curve below 72 GPa was fitted to the Birch-Murnaghan equation of state with V0=2023(19) Å3, K0=131(7) GPa, K′=4.0 (fixed). The resulting EoS parameters are approximately consistent with those observed in previous study. A discontinuous volume change is observed between 72 and 75 GPa. These observed results indicate a phase transition from i-AlCuFe QC to an approximant crystal (AC) which has a similar local atomic arrangement as the QC. This study suggests that i-AlCuFe QC maintains its structure at least up to 72 GPa and then transforms to AC with small displacement of atoms.