Site preference of Ru in NiAl and valence band structure of NiAl containing Ru: First-principles study and photoelectron spectrum

The site preference of Ru in NiAl was studied using first-principles calculations. The calculation of formation energies indicated that the site preference of Ru was on the Ni sites. The valence band (VB) structures of the NiAl alloys were investigated by photoelectron spectroscopy. The VB spectra of the NiAl-Ru alloy was shifted away from the Fermi level so that the Ni d-band centroid moved to a higher energy by 7.77 eV as Ru was added. Such a shift revealed that the Ni-Ru interactions gave a significant contribution to the VB structure of the NiAl-Ru alloy.