Charge transfer and hybridization effects in Ni3Al and Ni3Ga studies by x-ray-absorption spectroscopy and theoretical calculations

This work investigates the charge transfer and Al(Ga) p-Ni d hybridization effects in the intermetallic Ni3Al (Ni3Ga) alloy using the Ni L-3,L-2 and K edge and Al (Ga) K x-ray absorption near edge structure (XANES) measuremen ts. We find that the intensity of near-edge features at the Ni L-3 edge in the Ni3Al (Ni3Ga) alloy decreased with respect to that of pure Ni, which im plies a reduction of the number of unoccupied Ni 3d states and an enhanceme nt of the Ni 3d state filling in the Ni3Al (Ni3Ga) alloy. Two clear feature s are also observed in the Ni3Al (Ni3Ga) XANES spectrum at the Al (Ga) K ed ge, which can be assigned to unoccupied Al 3p-(Ga 4p-) derived states in Ni 3Al (Ni3Ga). The threshold at the Al K-edge XANES for Ni3Al shifts towards the higher photon energy relative to that of pure Al, suggesting that Al lo ses some p-orbital charge upon forming Ni3Al. On the other hand, the Ni K e dge shifts towards the lower photon energy in Ni3Al (Ni3Ga) relative to tha t of pure Ni, suggesting a gain of charge at the Ni site. Thus both Al and Ni K-edge XANES results imply a transfer of charge from Al 3p orbital to Ni sites. Our theoretical calculations using the spin-polarized first-princip les pseudofunction method agree with these results. (C) 2000 American Insti tute of Physics. [S0021-8979(00)03603-3].