Crystallisation of AlFe icosahedral quasicrystals under high pressures

Abstract

The observation of electron diffraction spots with 5-fold symmetry in rapidly quenched $Al_{86}Mn_{14}$ alloys (1) and subsequently in a few other alloys has created considerable interest. These materials, called Quasierystals, have been subjected to various studies. In addition to icosahedrai phases, decagonal phases have also been observed. A 5-fold symmetry is not compatible with any crystallographic arrangement. Therefore these alloy fragments are considered to have an aperiodic space filling arrangement with pentagonal symmetry (2), though the possibility of twinned structures (3) has also been advocated, Nevertheless the observation of phases with the forbidden 5-fold diffraction patterns is of considerable excitement as regards not only the atomic structure but also the physical properties.