Standard stereographic diagrams and indexing of X-ray Laue diffraction spots of an icosahedral quasicrystal

White-beam synchrotron-radiation X-ray topographs of the Al₆₂Cu_25.5Fe_12.5 icosahedral quasicrystal (IQC) have been taken for different specimen 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^||) has been calculated with the simple lattice model for each reciprocal vector g^|| with indices n_i^* lying in the range −8 ≤ n_i^* ≤ 8 and reflections with the highest S(g^||) values have been selected to simulate the geometric distribution of the Laue spots for a given incident-beam direction. On the basis of standard diagrams of simulated Laue patterns, all the strong diffraction spots have been indexed successfully. For the specific experimental arrangement and the characteristics of the synchrotron-radiation source, the mean intensities of the diffraction spots have been calculated and are in agreement with the experimental ones.