Al 3p occupied states in Al-Cu-Fe intermetallics and enhancedstability of the icosahedral quasicrystal

Abstract

This paper concentrates on a comparison of Al 3p occupied densities of statesin crystalline and quasicrystalline Al-Cu-Fe intermetallics. Thiscomparison is made quantitative by computing the two first moments of thispartial distribution, which correspond to the partial contribution of Al atomsto the cohesive energy of the material and to the orbital overlap modulated bythe coordination number, respectively. From these data, we conclude that theicosahedral quasicrystal and its approximants represent a region ofspecifically enhanced stability in the Al-Cu-Fe phase diagram. Weassign this effect to the specific role played by Al 3p states in theHume-Rothery mechanism. We confirm the occurrence of a stronger hybridizationbetween Al 3p and Fe 3d states in the icosahedral structure whereas we pointout a weaker interaction with Cu 3d states in the icosahedral compounds ascompared to stable approximants.