Electron low energy-loss functions of Pb(Mg1/3Nb2/3)O3:: Theory and experiment

Local low energy-loss functions (ELFs) of chemical ordered nanodomains in relaxor Pb(Mg1/3Nb2/3)O-3 (PMN) were obtained by using Kramers-Kronig analysis of experimental electron low energy-loss spectra. Electronic structures and dielectric functions were calculated via ab initio calculation using the full-potential linearized augmented plane-wave method on a 30 atom PMN supercell with B-site cation ordering along the [111] direction. The theoretical ELFs are fundamentally in agreement with the experimental ELFs. Furthermore, we systematically elucidate all the peaks in the low ELF based on the ab initio calculated densities of states. It is found that the Nb 4d-O 2p hybridization is enhanced through ferroelectric transition, which makes the O 2p collective excitation energy upper shift in ELF, while Mg, also as the B-site ion, presents no covalent bonding effect with O. (c) 2008 American Institute of Physics.