X-ray diffraction measurements in icosahedral Al-Pd-Mn up to 40 GPa

X-ray diffraction experiments have been performed in an Al-Pd-Mn quasicrystal under pressure up to 40 GPa. The icosahedral phase proved to be stable up to that pressure. Ultrasonic measurements of the bulk modulus B 0 and its pressure derivative B′0 are compared with X-ray diffraction data. Up to 15 GPa, a fairly good agreement between a Birch-Murnaghan equation of state, using B 0 and B′0 deduced from ultrasonic measurements, and the X-ray diffraction data can be observed, with a deviation less than 0.5%. The values of B 0 and of B′0 obtained by ultrasonic techniques are 128 GPa and 4.7 respectively and those deduced from the X-ray diffraction data are B 0 =133 ± 5GPa and B′0 =5 ± 1. Above 15 GPa, an increasing deviation between ultrasonic and X-ray diffraction measurements can be observed.