Single-crystal X-ray study of the decagonal phase of the system Al-Mn

A single crystal of the metastable decagonal phase of the system Al-Mn with the composition Alsub(0.78(2)-)Mn0.22(2) and approximate dimensions 0.25x0.13x0.08 mm3 has been investigated by various X-ray film methods and on a four-circle diffractometer. The diffraction pattern can be indexed using four reciprocal lattice vectors pointing to the vertices of a pentagon a1*=a2*=a3*=a4*=0.2556(1) A-1 and one normal to them parallel to the tenfold axis a5*=0.08065(5) A-1 [a5=12.400(7) A]. The X-ray photographs indicate that this two-dimensionally quasicrystalline phase is highly ordered. Nevertheless, a considerable amount of diffuse scattering is observed in the reciprocal lattice layers perpendicular to the tenfold axis. (orig.)