A synchrotron X-ray diffraction analysis of near-stoichiometric LiNbO3

Abstract

Abstract Single-crystal diffraction data was collected at 120 and 294 K for an approximately spherical LiNbO3 crystal, 16 μm in diameter, using focused λ=0.7516 (1) Å wavelength synchrotron X-radiation and a fast avalanche photodiode (APD) detector. Extinction was significantly less than that recorded for previous single-crystal X-ray diffraction experiments. Anharmonic atomic displacements of Nb and Li were refined using a Gram-Charlier expansion to the fourth order. There was no significant change in the topography of the difference electron density (Δρ) map after anharmonic refinement. An accumulation of electrons present at the vacant site in the 294 K Δρ map was not evident in the 120 K Δρ map, indicating a migration of Li atoms to the vacant site as the temperature increased. The orientation of the electron density around Nb flipped by 90° going from 120 to 294 K.