About the Al 3p density of states in Al–Cu–Fe compounds and its relation to the compound stability and apparent surface energy of quasicrystals

We report the characteristic parameters of the Al 3p densities of states gained from a thorough study of many Al–Cu(–Fe) intermetallics including quasicrystalline and approximant phases using X-ray emission spectroscopy. These parameters are the density of states at the Fermi energy EF, the average binding energy due to Al 3p states and the second moment of their distribution. Hence, we demonstrate that the contribution to the compound stability arising from localization of Al 3p states via the Hume-Rothery mechanism is maximum for the icosahedral state. We also show that Al-transition metal sp-d hybridization is enhanced in the presence of icosahedral order. Finally, we confirm the already pointed out relationship between depth of the pseudo-gap at EF and apparent surface energy of the samples.