Electronic structure of NiAl

Resonance Photoemission at the 2p Excitation Threshold of Ni3Al

A marked resonance enhancement of the 3d photoemission intensity in angle-integrated electron-distribution curves from Ni3Al has been observed 6.6 eV below the Fermi level for photon energies in the vicinity of the Ni 2p absorption threshold. Soft x-ray L-edge absorption spectra were measured to determine the Ni 2p excitation threshold. The Fano asymmetry parameter and the effective Coulomb interaction for Ni3Al are 2.2 and 4.8 eV, respectively, as derived from the experimental data. Differences between the 2p→3d and the 3p→3d resonance effect are discussed, and comparisons with Ni, NiAl, and NiGa are made.

Density functional theory study of H and H2 interacting with NiAl(110)

We present results of extensive density functional theory (DFT) calculations for H and H2 interacting with NiAl(110). Continuous representations of the full dimensional potential energy surface (PES) for the H/NiAl(110) and H2/NiAl(110) systems are obtained by interpolation of the DFT results using the corrugation reducing procedure. We find a minimum activation energy barrier of approximately 300 meV for dissociative adsorption of H2, which is consistent with the energy threshold obtained in molecular beam experiments for H2 (nu=0). We explain vibrational enhancement observed in experiments as the consequence of vibrational softening in the entrance channel over the most reactive surface site. The H2/NiAl(110) PES shows a high surface site selectivity: for energies up to 0.1 eV above threshold, H2 adsorption can only take place around top-Ni sites (within a circle of radius approximately 0.3 A). A strong energetic corrugation is observed: energy barriers for dissociation vary by more than 1 eV between the most and the least reactive sites. In contrast, geometric corrugation is much less pronounced and comparable to that of low index single metal surfaces like Cu or Pt.