First-Principles Approach to Extracting Chemical Information from X‑ray Absorption Near-Edge Spectra of Ga-Containing Materials

The
X-ray absorption near-edge structure (XANES) can provide uniquely
detailed information on the coordination environments of important
Ga-containing materials with unknown structures, including catalytically
active materials. In this study, the Ga K-edge XANES was simulated
using first-principles-based methods for seven molecular Ga complexes
as well β-Ga2O3, in order to explore the
chemical origins of the experimentally observed features. The theoretical
spectra were computed using FEFF, CASTEP, and StoBe, to assess the
sensitivity of the results to the computational approach. While the
XANES features depend on the Ga coordination environment, they are
also sensitive to the electronegativity of the ligands and the symmetry
at Ga. The white line position responds to changes in both the core
state (due to differential screening) and the valence “p”
states (arising from differences in ligand coordination).