REAL-SPACE ANALYSIS OF PHASON DISORDERS IN DECAGONAL QUASI-CRYSTALS

We propose a method for real space analysis of phason disorder based o n high-resolution electron microscopy (HREM) images of decagonal quasi crystals (DQCs). The position vectors of the centres of the ring contr asts on a 2 nm scale are indexed first with four basis vectors which a re four of the five vertex vectors of a regular pentagon. The strain t ensor of the linear phason is extracted from the set of indexed vector s. We applied our method to AlNiCo and AlPdMn photographed by Hiraga e t al, and found that the linear phason in AlNiCo is very weak but that in AlPdMn is much stronger. Both the DQCs include considerable amount s of random phasons. These phason disorders are, however, very few on the atomic scale. The AlNiCo sample is an almost ideal DQC on the atom ic scale. Our method detects sensitively phason disorders.