Electronic structures and cohesion mechanism of Cd-based quasicrystals

Electronic structures of cubic Cd6M (M = Yb, Ca and Mg), which are approximant phases of newly discovered Cd-based quasicrystals, are studied by the tight-binding linear muffin-tin orbitals method. It is found that stabilization due to alloying is obtained when M is an element with low-lying unoccupied d states. Although a shallow dip in the density of states appears near the Fermi level and the diameter of the Fermi sphere coincides with the (222100) and (311111) reciprocal lattice vectors, the Brillouin-zone-Fermi-sphere interaction does not play a principal role in the Cd-based systems, because neither a distinct dip nor additional stabilization due to alloying is obtained for isostructural Cd-Mg. These observations lead to the conclusion that the cohesion of the Cd-based compounds is certainly due to the hybridization of the d states of Yb/Ca with a wide sp band. (C) 2002 Elsevier Science B.V. All rights reserved.