Theoretical investigation of the ELNES of transition metal carbides for the extraction of structural and bonding information

Abstract

We present the results of theoretical modeling studies of the electron energy loss near-edge structure (ELNES) of Group-IVA (Ti, Zr, Hf) and Group-VA (V, Nb, Ta) transition-metal carbides exhibiting a cubic NaCl structure. Calculations of the unoccupied densities of states at both metal and nonmetal sites have been performed using both multiple scattering (MS) and full linearized-augmented-plane-wave (FLAPW) band-structure calculations. The effects of self-consistency and the inclusion of the core hole produced during the ELNES excitation process have been investigated for the case of the MS calculations, while the size of the basis set and the effect of charge transfer have been examined for the case of the FLAPW calculations. The results are compared to high-energy-resolution ELNES measurements. We demonstrate the sensitivity of ELNES features to quantities such as the lattice parameter, chemical composition, and stoichiometry.