Modulated quasicrystal structures

A model for the formation of modulated structures frequently observed in icosahedral alloys of the Al‒Cu‒Fe type and representing an intermediate phase at the icosahedral phase-crystalline approximant transition is proposed. An assumption that this structural modulation may be due to a weak decagonality of the icosahedral phase is advanced. In our model, two different types of modulated structure can be distinguished. Such a decagonality originating both from phason strains and from a probable anisotropy of icosahedral shells has been considered.