Experimental study of the dynamics of icosahedral phases

We review experimental results obtained in the study of the dynamics of icosahedral phases by mean of inelastic neutron and X-ray scattering on single grains of the i-AlPdMn, i-ZnMgY and i-CdYb phases. Although the three phases have very different atomic structures and sound velocities, for all of them we observe two distinct regions. For small wave vectors (q<0.3 Å−1) there are well defined acoustic modes, whereas there is a series of broad dispersionless optic-like excitations at higher energy. The cross-over between the two regions is abrupt. However the detail of the interaction between acoustic modes and optic excitations depends strongly depending on the atomic structure.