STANDARD STEREOGRAPHIC DIAGRAMS AND INDEXING OF X-RAY LAUE DIFFRACTION SPOTS OF AN ICOSAHEDRAL QUASI-CRYSTAL

White-beam synchrotron-radiation X-ray topographs of the Al62Cu25.5Fel 2.5 icosahedral quasicrystal (IQC) have been taken for different speci men orientations. Standard stereographic projection diagrams along the two-, three-, and fivefold zone axes of the IQC have been calculated by the cut-and-projection method. The total structure factor S(g paral lel-to) has been calculated with the simple lattice model for each rec iprocal vector g\\ with indices n(i) lying in the range - 8 less-than -or-equal-to n(i) less-than-or-equal-to 8 and reflections with the hi ghest S(g parallel-to) values have been selected to simulate the geome tric distribution of the Laue spots for a given incident-beam directio n. On the basis of standard diagrams of simulated Laue patterns, all t he strong diffraction spots have been indexed successfully. For the sp ecific experimental arrangement and the characteristics of the synchro tron-radiation source, the mean intensities of the diffraction spots h ave been calculated and are in agreement with the experimental ones.