Quasicrystal with One-Dimensional Translational Symmetry and a Tenfold Rotation Axis

Studies of phase formation in rapidly solidified Al-Mn alloys (composition range 18-22 at. % Mn) show that an icosahedral phase is replaced by another noncrystallographic phase, a decagonal phase. The decagonal phase is another example of quasicrystal: It has a noncrystallographic point group (10m or 10mmm) together with long-range orientational order and one-dimensional translational symmetry. The decagonal phase is an intermediate phase between an icosahedral phase and a crystal both from the symmetry and from the solidification condition points of view.