Electron Localization and Structural Distortions in the Metal-Insulator Transition of Simple Oxides

6 pages, 7 figures.-- Communication presented at the 6th World Multiconference on Systemics, Cybernetics and Informatics and 8th International Conference on Information System Analysis and Synthesis (SCI/ISAS 2002, Orlando, Florida, Jul 14-18, 2002).
We report on electron-phonon interactions as a main common property in simple oxides deduced from infrared measurements, and search, using X-ray absorption techniques, a local structure counterpart associated to it. We found that temperature dependent electron localization is determinant in explaining the conductivity in RNiO3 (R= rare earth) and in La(0.67)Ca(0.33)MnO3 and their metal-insulator phase transitions. This is also associated to a lower symmetry lattice distortion in the insulating phase. The mechanism established from comparison of the experimental conductivity obtained from reflectivity spectra with that from Reik’s theory [1] suggests small polaron hopping as the principle for electron displacement in an oxygen high polarizable lattice. We also comment our preliminary results on the temperature dependent consequence of Jahn- Teller and GdFeO3 lattice distortions in the insulator YVO3.