THE DEVIATIONS OF THE AL6LI3CU QUASI-CRYSTAL FROM ICOSAHEDRAL SYMMETRY - A REMINISCENCE OF A CUBIC-CRYSTAL

The Al6Li3Cu (T2) quasicrystals are known to exhibit large deviations from the icosahedral symmetry. Series of electron diffraction patterns are used to investigate these imperfections in as-cast T2 samples. A detailed analysis of the 5-fold and 3-fold symmetry diffraction patter ns shows that they are compatible with the m3 point group instead of t he m35 icosahedral group. This symmetry reduction is interpreted as re miniscent of the cubic approximant phase (R-Al5Li3Cu) rather than of h igher order approximant phases. This interpretation is supported by pr evious observations on crystal/quasicrystal phase transformation in th e AlLiCu system.