Phonon dynamics in 3D quasicrystals versus amorphous solids

Abstract

Quasicrystals (QCs) possess a unique long-range quasi-periodic order distinct from both crystalline and amorphous solids. The vibrational properties of QCs remain poorly unexplored. Here, we employed classical molecular dynamics simulations to investigate the phonon dynamics of a 3D single-component icosahedral QC model and a Kob–Andersen (KA) glass model. By comparing the vibrational density of state (VDOS), phonon dispersion, and phonon lifetime, we elucidate the impact of structural order on the phonon dynamics. Although QC shows similar phonon dynamics to amorphous solid rather than crystals, our findings reveal significant differences between the two systems. The VDOS of the QC exhibits a double-peak feature and a “fake” boson peak compared to the KA glass. The phonon dispersion in the QC displays more pronounced elastic anisotropy, with well-defined transverse and longitudinal modes, unlike the more isotropic dispersion in the KA glass. Moreover, the correlation between the transverse phonon linewidth and the structure factor, observed in the KA glass, is absent in the QC. Phonon lifetimes in the QC are generally longer than in the KA glass, with a faster decay rate. This comparative study highlights the distinctive vibrational properties of 3D QCs, emphasizing the role of structural order in determining phonon behaviors in solids.