CHARACTERIZATION OF 3D TRANSITION-METAL DIBORIDES BY X-RAY-ABSORPTION SPECTRA AT THE METAL K EDGE

The 3d transition-metal diborides TiB2, VB2 and CrB2 have been characterized by X-ray absorption near-edge-structure (XANES) spectroscopy at the metal K edges. XANES spectra at the Ti, V and CrK-edges of TiB2, VB2 and CrB2, respectively, show similar spectral features up to an energy of about 70 eV above threshold. These features can be correlated to their specific atomic arrangement and electronic structure via multiple-scattering calculations as a function of the cluster size. Actually the second pre-edge feature is assigned to a transition from the metal 1s core state to the central metal 4p state hybridized with 3d band state of the higher-shell metal atoms. The first weak feature on the rising part of the edge is due to higher-shells multiple scattering contributions, suggesting that the transition features at the metal K-edge XANES of 3d transition-metal diborides are strongly affected by medium or long-range order contributions.