Al13M4-type structures and atomic models of their twins

From the structural analysis of Al13Fe4 and Al13Co4 phases as well as a new Al13(Pd, Fe)4 phase with single-crystal X-ray diffraction, their structures were examined in terms of tilings of two types of pentagonal columns, which have similar atomic arrangements in the three phases. It has been found that the tilings of the pentagonal columns in these phases are characterized as arrangements of squashed hexagonal tiles formed by an edge-sharing linkage of the pentagonal columns, and that there is a rule for arrangements of the pentagonal columns forming the hexagonal tiles. It has been found from high-resolution electron microscopy observations that the structures of twins in the three phases can be interpreted by this topological rule for arrangements of the pentagonal columns.