Probing the electronic structure of complex crystals with electron energy loss spectroscopy: a study of natisites

The energy loss near edge structure (ELNES) of the O K and Ti L23 edges recorded in two compounds with the natisite structure, namely Li2TiOSiO4 and Li2TiOGeO4, are interpreted using ab initio band structure and ligand-field multiplet calculations. The origin of the different peaks observed in the experimental O K edge is discussed in terms of chemical bonding between the O atoms and their Ti and Si (Ge) nearest neighbours. In particular, the high sensitivity of the O K edge to the square pyramidal geometry of the Ti atomic site is underlined and correlated to the signature observed on the Ti L23 edge. We demonstrate here the ability of electron energy loss spectroscopy to investigate the chemical and structural environment of atoms in complex compounds.