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Structural model and electronic structure of the icosahedral Al − Ga − Pd − Mn quasicrystal

2005; American Physical Society; Volume: 72; Issue: 9 Linguagem: Inglês

10.1103/physrevb.72.092203

1550-235X

Eeuwe S. Zijlstra, S. K. Bose, J. Dolinšek,

Advanced Chemical Physics Studies

The structural model and the electronic structure of a newly discovered $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Ga}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ icosahedral quasicrystal with composition ${\mathrm{Al}}_{67}{\mathrm{Ga}}_{4}{\mathrm{Pd}}_{21}{\mathrm{Mn}}_{8}$ were studied by density functional methods. Calculations are based on the Quandt-Elser periodic approximant model of $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$, which was fully relaxed. To determine which Al sites in the $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Ga}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ are occupied by Ga, total energies were compared, showing that Ga substitutes two of the aluminum glue atoms, ${\mathrm{Al}}_{5}$ and ${\mathrm{Al}}_{6}$, but no Al atoms that are part of a Bergman cluster. Since only specific Al sites are substituted by Ga, $i\ensuremath{-}\mathrm{Al}\ensuremath{-}\mathrm{Ga}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ is predicted to be a true quaternary quasicrystal, structurally isomorphous with $i\ensuremath{-}\mathrm{Al}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$. Calculation of the electronic density of states of $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Ga}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ and its comparison to $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ predicts that 4% $\mathrm{Al}\ensuremath{\rightarrow}\mathrm{Ga}$ substitution in the $i\text{\ensuremath{-}}\mathrm{Al}\ensuremath{-}\mathrm{Pd}\ensuremath{-}\mathrm{Mn}$ lattice should have negligible influence on the electronic properties of this quasicrystal.