Narrow Results

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.

The following sections are included:

• Introduction

• Unified MS XAFS and NEXAFS Calculations
  • Curved Wave Scattering Theory
  • Path Filters
  • Scattering Potentials
  • Self-energy and Mean Free Path
  • Thermal and Configurational Disorder

• Applications to XAFS and XANES
  • Information Content in XAFS
  • Example of MS XAFS Calculation
  • NEXAFS and Shape Resonances
  • Application to XANES

• Conclusions

• Acknowledgments

• References

X-ray absorption fine structure (XAFS) spectroscopy has been widely used for decades in a wide range of scientific fields, including physics, chemistry, biology, materials, environmental sciences, and so on. In this chapter, we introduce the XAFS principles, including its basic theory, data analysis and experiment, from the view point of practical use. To show its strength as a local structure probe, applications of XAFS in various functional materials are introduced, covering nanoparticles and catalysts, magnetic semiconductors, thin film materials, complex compounds, in situ probing of the nucleation and growth processes of nanomaterials, as well as operando study of catalysts under working conditions.

In addition, we also briefly introduce some relatively new XAFS-related techniques, such as time-resolved and space-resolved XAFS techniques.