NEW CRYSTALLINE APPROXIMANT OF THE DECAGONAL QUASI-CRYSTAL IN AL-PD-RU ALLOY

A new crystalline approximant of the Al-Pd-type decagonal quasicrystal with composition Al75Pd13Ru12 has been discovered and studied by mean s of X-ray single-crystal and powder diffraction techniques. The phase has a base-centred orthorhombic unit cell with lattice parameters a = 2.3889(3) nm, b = 3.2802(3) nm and c = 1.6692(1)nm. The diffraction p atterns show that fivefold rotational twinning occurs frequently in th e samples. The twin mechanics is explained by a tiling model of the Al 75Pd13Ru12 phase, which is composed of hexagonal and crown-shaped tile s.