Core-hole effect in the ELNES of alpha-Al2O3: experiment and theory

The occurrence of the core-hole effect at the AI-K and Al-L-1 edge in alpha -Al2O3 was studied by comparing experimental electron energy-loss near-edg e structures (ELNES) and results of band-structure calculations with and wi thout accounting for core-hole effects by the Z + 1 approximation. It was f ound that the theoretically calculated unoccupied p-like projected densitie s of states (PDOS) without Z + 1 approximation matches better to the experi mental Al-L-1 ELNES, whereas the PDOS with Z + 1 approximation matches bett er to the experimental AI-K ELNES. We conclude that the localisation of the initial state is an important prerequisite for the observability of the co re-hole effect in the ELNES. (C) 2001 Elsevier Science B.V. All rights rese rved.