Various features of quasicrystal diffraction patterns are discussed. The projection scheme is used throughout and applied in some detail to the pattern formed by icosahedral Al-Mn. Comparison with the diffraction pattern formed by the vertices of a three-dimensional Penrose tiling leads to the value 4.60 Å for the rhombohedron edge length.

• Received 26 April 1985

DOI:https://doi.org/10.1103/PhysRevB.32.4892