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

Abstract

This work investigates the charge transfer and Al(Ga) p-Ni d hybridization effects in the intermetallic Ni3Al (Ni3Ga) alloy using the Ni L3,2 and K edge and Al (Ga) K x-ray absorption near edge structure (XANES) measurements. We find that the intensity of near-edge features at the Ni L3 edge in the Ni3Al (Ni3Ga) alloy decreased with respect to that of pure Ni, which implies a reduction of the number of unoccupied Ni 3d states and an enhancement of the Ni 3d state filling in the Ni3Al (Ni3Ga) alloy. Two clear features are also observed in the Ni3Al (Ni3Ga) XANES spectrum at the Al (Ga) K edge, which can be assigned to unoccupied Al 3p-(Ga 4p-) derived states in Ni3Al (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 loses some p-orbital charge upon forming Ni3Al. On the other hand, the Ni K edge shifts towards the lower photon energy in Ni3Al (Ni3Ga) relative to that 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-principles pseudofunction method agree with these results.