Al13M4-type structures and atomic models of their twins

From the structural analysis of Al13Fe4 and Al13Co4 phases as well as a new Al-13(Pd, Fe)(4) phase with single-crystal X-ray diffraction, their struct ures were examined in terms of tilings of two types of pentagonal columns, which have similar atomic arrangements in the three phases. It has been fou nd that the tilings of the pentagonal columns in these phases are character ized as arrangements of squashed hexagonal tiles formed by an edge-sharing linkage of the pentagonal columns, and that there is a rule for arrangement s of the pentagonal columns forming the hexagonal tiles. It has been found from high-resolution electron microscopy observations that the structures o f twins in the three phases can be interpreted by this topological rule for arrangements of the pentagonal columns. (C) 2000 Elsevier Science B.V. All rights reserved.