Discommensurate microstructures in phason-strained octagonal quasicrystal phases of Mo-Cr-Ni.

Abstract

Phason-strained octagonal quasicrystal phases of Mo-Cr-Ni have been studied by electron diffraction and dark-field imaging. Diffraction patterns of the twofold axes show that some spots are shifted and split along the fourfold axis. Discommensurations (DCs) observed in dark-field images of the split reflections are aligned perpendicular to the fourfold axis. The density of the DCs in widely separated and adjacent regions may vary by more than 1 order of magnitude. Our observations are consistent with some of the results of the two-dimensional octagonal random tiling model of Li, Park, and Widom.