Experimental Study Of Phonon Dynamics In The Icosahedral I-Cdyb Phase And Its 1/1 Periodic Approximant

We report on a comparative dynamical study carried out by inelastic X-ray scattering on the i-Cd5.7Yb quasicrystal and on its 1/1 approximant Cd6Yb. The phonon response function is shown to be very similar in both systems, with well defined acoustic modes for small wavevector values and dispersionless optical bands centred around 4, 9 and 16 meV. However the acoustic regime is found to be more limited in the i-phase.