Atomic arrangements in quasicrystals

Abstract

The discovery of the first quasicrystals in 1984, the studies of their formation in different alloys and the attempts to understand the atomic arrangement in them, are discussed. After highlighting the important experimental observations on these new phases, the proposed models for their atomic structure are considered, under the heads of 3-dimensional Penrose tiling (3-DPT), dense packing of icosahedra (DPI), multiple twinning (MT) and periodic pentagonal chains (PPC). While the MT model does not seem to have strong experimental backing, there seems to be good agreement between diffraction theory and practice in case of both the 3-DPT and DPI models. The PPC model is shown to have the potential to explain the close inter-relationship existing between the liquid, quasicrystalline and glassy phases in concerned alloys.