Dynamic properties of Al-Ni-Co decagonal quasicrystals modelled by ab initio interatomic pair potentials

Vibrational spectra of realistic structural models for ternary Al-Ni-Co decagonal quasicrystals are studied. A bunch of dispersion-less modes is obtained above a few meV, which is extremely low in comparison with usual optic modes. Analyzing the local vibrational density of states at an individual atomic site, we identify several Al sites where low- and high-frequency vibrations are localized. The localized vibrations are attributed to the strong Al-TM interaction and the local atomic arrangements realized in the complex structures. Low-frequency dispersion-less modes are of special interest in relation to the phason degrees of freedom in QC but no signature of large atomic motion causing the phasonic tile flip is obtained in the low-frequency localized vibrational modes.