New type of two-dimensional quasicrystal with twelvefold rotational symmetry

A 2D quasicrystal with a twelvefold rotational axis has been found in rapidly solidified ${\mathrm{V}}_{3}$${\mathrm{Ni}}_{2}$ and ${\mathrm{V}}_{15}$${\mathrm{Ni}}_{10}$Si alloys by means of transmission electron microscopy. The electron diffraction pattern taken along this axis shows no periodicity but a clear twelvefold orientation symmetry. The corresponding high-resolution electron-microscopic image agrees well with an aperiodic pattern consisting of squares and equilateral triangles. A structural model for this dodecagonal quasicrystal has been proposed.