Structure of icosahedral clusters in cubicAl5.6Li2.9Cu

Abstract

We present a structure refinement of crystalline ${\mathrm{Al}}_{5.6}$ ${\mathrm{Li}}_{2.9}$Cu based on x-ray and neutron-diffraction data. We find that clusters of atoms form nearly ideal icosahedra in a bcc lattice, with different positions and occupancies than those proposed in previous work. Since neutrons and x rays have very different scattering amplitudes for Al, Li, and Cu, and since their respective diffraction profiles therefore consist of different peak intensities, the close agreement of the structural parameters from the two fits is a strong argument for the correctness of our results. These should be useful in packing-model descriptions of the related icosahedral phase.