Hybridization Mechanism for Cohesion of Cd-based Quasicrystals
  Cohesion mechanism of cubic approximant crystals of newly discovered binary quasicrystals, Cd$_6$M (M=Yb and Ca), are studied theoretically. It is found that stabilization due to alloying is obtained if M is an element with low-lying unoccupied $d$ states. This leads to conclusion that the cohesion of the Cd-based compounds is due to the hybridization of the $d$ states of Yb and Ca with a wide $sp$ band. %unlike known stable quasicrystals without transition elements %such as Al-Li-Cu and Zn-Mg-RE (RE:rare earth). Although a diameter of the Fermi sphere coincides with the strong Bragg peaks for Cd-Yb and Cd-Ca, the Hume-Rothery mechanism does not play a principal role in the stability because neither distinct pseudogap nor stabilization due to alloying is obtained for isostructural Cd-Mg. In addition to the electronic origin, matching of the atomic size is very crucial for the quasicrystal formation of the Cd-based compounds. It is suggested that the glue atoms, which do not participate in the icosahedral cluster, play an important role in stabilization of the compound. 
Yasushi Ishii and Takeo Fujiwara