Electron diffraction studies of variable periodicity in decagonal quasicrystals in aluminium-cobalt alloys

The reciprocal space vectors of the decagonal phase can be generated by a slight distortion of the basis vectors of a regular icosahedron to induce commensuration in one dimension. In different alloys a multiple of this basic periodicity has been observed. In particular, in Al-Co alloys, apart from the basic periodicity, doubling, tripling and quadrupling of this basic underlying periodicity has been observed. Stereographic analysis, simulation and experimental observation of electron diffraction patterns have been used to explore the nature of this varying periodicity in detail