Lattice dynamics of the Zn-Mg-Sc icosahedral quasicrystal and its Zn-Sc periodic 1/1 approximant

de Boissieu, M.*; Francoual, S.*; Minalkovi, M.*; Shibata, Kaoru  ; Baron, A. Q. R.*; Sidis, Y.*; Ishimasa, Tsutomu*; Wu, D.*; Lograsso, T.*; Regnault, L.-P.*; Ghler, F.*; Tsutsui, Satoshi*; Hennion, B.*; Bastie, P.*; Sato, Taku*; Takakura, Hiroyuki*; Currat, R.*; Tsai, A.-P.*

We have carried out inelastic X-ray and neutron scattering experiments on single-grain samples of the Zn-Mg-Sc icosahedral quasicrystal and of the Zn-Sc periodic cubic 1/1 approximant, with the aim of studying the respective influence of the local order and the long-range order (periodic or quasiperiodic) on lattice dynamics. Besides the overall similarities and the existence of a pseudo-gap in the transverse dispersion relation, marked difference are observed, the pseudo-gap being larger and better defined in the approximant than in the quasicrystal. These results are compared with simulations on atomic models and using oscillating pair potentials, and the simulations reproduce in detail the experimental results.