Spectroscopic study on chemical ordering of transition metals in decagonal Al-Co-Ni and Al-Co-Cu quasicrystals

Preferred occupation at the transition metal (TM) sites in the building unit cluster of two-dimensional Al-Co-Ni and Al-Co-Cu quasicrystals has been investigated by comparing their experimental electronic structures with those of the unit clusters calculated by a discrete variational Xa method. Analysis of the bonding character and bond energy for local clusters around the TM sites shows that the Al-Co-Cu quasicrystal favours the Cu and Co occupations at the first and second inner TM sites, respectively, and hence the chemical order of these TM's, while the small bond energy difference in the Ni and Co occupations at those TM sites suggests the large chemical disorder of the transition metals in the Al-Co-Ni quasicrystal.