Pressure–Volume Relationship of a Au–Al–Yb Intermediate Valence Quasicrystal and Its Crystalline Approximant

Synchrotron X-ray diffraction experiments of an icosahedral Au–Al–Yb quasicrystal and its 1/1 crystalline approximant were performed under quasi-hydrostatic pressure up to approximately 20 GPa at room temperature. Their pressure–volume compression curves are similar to each other, and show a monotonic decrease, which indicates the structural stability of these compounds under pressure. The bulk moduli were determined to be B0 = 105.1(8) GPa for the quasicrystal and B0 = 108.1(7) GPa for the crystalline approximant. These values are explained by the composition-weighted average of the bulk moduli of each constituent element.