Al 3p occupied states in Al-Cu-Fe intermetallics and enhanced stability ofthe icosahedral quasicrystal

This paper concentrates on a comparison of Al 3p occupied densities of star es in crystalline and quasicrystalline Al-Cu-Fe intermetallics. This compar ison is made quantitative by computing the two first moments of this partia l distribution, which correspond to the partial contribution of Al atoms to the cohesive energy of the material and to the orbital overlap modulated b y the coordination number, respectively. From these data, we conclude that the icosahedral quasicrystal and its approximants represent a region of spe cifically enhanced stability in the Al-Cu-Fe phase diagram. We assign this effect to the specific role played by Al 3p states in the Hume-Rothery mech anism. We confirm the occurrence of a stronger hybridization between Al 3p and Fe 3d states in the icosahedral structure whereas we point out a weaker interaction with Cu 3d states in the icosahedral compounds as compared to stable approximants.