SINGLE-CRYSTAL NEUTRON-DIFFRACTION OF DECAGONAL AL72.5CO11NI16.5

A single crystal of the thermodynamically stable decagonal phase in th e system Al-Ni-Co with the nominal composition Al72.5CO11Ni16.5 was fi rst studied by neutron diffraction. The diffraction experiment showed that the investigated crystal was a true single crystal. In a prelimin ary experiment we have measured a selection of Bragg reflections, diff use scattering and satellite scattering and compared the observations with corresponding X-ray results. From this comparison we may conclude , that the 10mm symmetry is not due to the indiscernibility of Co and Ni atoms (X-rays), but a true structure feature. The superorder satell ite scattering is basically not due to a Co/Ni ordering problem.