Phonon–Phason Coupling Strength in a Tsai-Type Ag–In–Yb Icosahedral Quasicrystal

Abstract

Owing to the quasiperiodic order, one independent term in the elasticity of quasicrystals (phonon-phason coupling) is characteristic of quasicrystals. It is not seen in conventional crystals and has continued to be a significant subject in the research field of quasicrystals.Recently, a novel method was applied to a Mackay-type Al-Pd-Mn icosahedral quasicrystal to prove the existence of phonon-phason coupling and to evaluate its strength based on the elasticity of quasicrystals. This study applied the method to a Tsai-type Ag-In-Yb icosahedral system to evaluate its phonon-phason coupling strength. We applied phonon strain to the quasicrystal at a temperature with active phason, and the induction of phason strain was successfully detected and evaluated using powder X-ray diffraction. We evaluated the phonon-phason coupling elastic constant of the Ag-In-Yb icosahedral quasicrystal to be 0.17 ± 0.04 GPa by quantitatively comparing the measured induced phason strain with our calculation results.