Electronic structure of NiAl

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Abstract
The valence-band structure of nickel aluminum was measured by use of angle-resolved photoemission with synchrotron radiation and calculated using the local-density approximation. The overall agreement between theory and experiment is remarkably good—much better than for pure nickel. This means that the ‘‘self-energy’’ corrections are significantly less in NiAl than in pure nickel. The core-level binding energies in NiAl are compared experimentally and theoretically with the equivalent levels in Ni and Al. Surprisingly, the Ni core shifts to higher binding energy and the Al to lower as if charge were transferred from Ni to Al—opposite to the direction predicted from electronegativity. These observations are discussed in terms of bonding in NiAl.