Ab initio studies on chemical bonding in Cd- and Zn-based quasicrystals

Abstract Large clusters with successive atomic shells of icosahedral symmetry are believed to be basic structural units of the newly discovered binary Cd–M (M=Yb and Ca) and ternary Zn–Mg–Sc quasicrystals. The electronic structures of approximants Cd 6 M (M=Ca) and Zn 17 Sc 3 have been analyzed from a viewpoint of chemical bonding between atoms and clusters. It is found that the bonding nature changes from bonding to anti-bonding near the Fermi level for pairs of Cd/Zn atoms in the different atomic shells of a cluster. The Fermi level is located at the most optimal position for divalent M=Ca and substitution of a trivalent element for Ca causes partial occupation of the anti-bonding states. Consequently the substitution weakens the chemical bonding which favors the shell structure and linkage of the clusters.