Structural studies on photoactivated transition metal complexes

Abstract

Microsymposia C176diffuse scattering intensity around and between diffraction spots.The collected data of high quality can be used for further determination of a 3D crystal structure. For example, it was possible to identify all oxygen atoms in the calculated three-dimensional potential map after the crystal structure analysis of the experimental 3D data, collected using the rotation diffraction tomography method applied to K 2 Nb 14 O 36 sample (space group P4/mbm, unit cell is a = b = 27.5 Å, c = 3.94 Å). This is the first time for the given structure when the oxygen atoms have been localized and identified in the 3D potential map using electron microscopy.The use of cryo-TEM specimen holder allowed us to collect a data set and perform a partial reconstruction of a small part of reciprocal space for a sucrose sample. It was possible to maintain the data collection for ~12 min covering 16.5° in reciprocal space using 3D tomography. Electrostatic potential analysis of the rhombohedral phase of ferroelectric BaTiO 3 using CBED Kenji Tsuda, Rikiya Sano, Michiyoshi Tanaka, IMRAM, Tohoku University, Sendai (Japan). E-mail: k_tsuda@tagen.tohoku.ac.jp A CBED structure analysis method using convergent-beam electron diffraction developed by Tsuda and Tanaka [1, 2] enables accurate determination of crystal structural parameters such as atom positions, atomic displacement parameters (ADPs) and loworder structure factors from nanometer-sized specimen areas. From the refined parameters, electrostatic potential and electron density distributions are reconstructed. Recently, the method was successfully applied to the electrostatic potential analyses of silicon [3] and the orbital ordered phase of spinel oxide FeCr 2 O 4 [4].The method is particularly advantageous for the analysis of ferroelectric materials: (1) Reliable diffraction intensity data are obtained from a single ferroelectric-domain area of specimens containing minute ferroelectric domains. (2) The direction of ferroelectric polarization can be readily identified from the symmetries of CBED patterns through strong dynamical diffraction effect. (3) Electric polarization can be evaluated from the electrostatic potential distribution directly determined by the CBED analysis.In the present study, the structure analysis method has been applied to the rhombohedral phase of ferroelectric BaTiO 3 . CBED analysis of the tetragonal phase of ferroelectric BaTiO 3 at room temperature has not yet been successful enough. This could be attributed to the existence of partial disorder, or local fluctuations of atomic displacements which cause electric polarizations [5]. Such fluctuations are expected to be much smaller in the rhombohedral phase below 183 K.Energy-filtered CBED patterns of the rhombohedral phase were obtained at 90K using a JEM-2010FEF energy-filter transmission electron microscope operated at an accelerating voltage of 100 kV and a liquid-nitrogen cooling specimen holder. Two dimensional intensity data of reflection disks of the energy-filtered CBED patterns were ...