Noncentrosymmetric Structure of a Decagonal Al70Mn17Pd13Quasicrystal

A noncentrosymmetric structure of decagonal Al70Mn17Pd13 with the space group P10_5mc was determined for the first time on the basis of a single-crystal 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 the introduction of the shift from an ideal atom position. The structure loses the inversion center mainly by the breakdown of the mirror plane perpendicular to the tenfold axis which is caused by the asymmetric chemical arrangement.