Noncentrosymmetric structure of a decagonal Al70Mn17Pd13 quasicrystal

A noncentrosymmetric structure of decagonal Al70Mn17Pd13 With the space gro up P10(5)mc was determined for the first time on the basis of a single-crys tal X-ray data set. This analysis gave a considerable improvement over the corresponding centrosymmetric model [Weber & Yamamoto (1997). Philos. Mag. A76, 85-106]. For 1428 independent reflections, R-w = 0.119 (R = 0.167) and a reasonable chemical composition of Al69.1Mn18.5Pd12.4 was obtained by th e introduction of the shift from an ideal atom position. The structure lose s the inversion center mainly by the breakdown of the mirror plane perpendi cular to the tenfold axis which is caused by the asymmetric chemical arrang ement.