Applications of automated diffraction tomography (ADT) on nanocrystalline porous materials

Many porous materials, both inorganic and hybrid organic-inorganic, can only be synthesized as nanocrystals. X-ray powder diffraction delivers one-dimensional data from the overall sample and is therefore often limited by peak overlap at low or medium resolution and by peak broadening. Thus, structure solution of materials with large unit cells and low symmetry, disorder or pseudosymmetry, or available only in polyphasic systems, turns out to be problematic or even impossible. Electron diffraction allows collecting three-dimensional structure information from nanocrystalline materials, but is traditionally biased by low completeness of the diffraction data, dynamical scattering and beam damage. Recently, these limits have been significantly reduced by the development of automated diffraction tomography, a new method for electron diffraction data acquisition and analysis. In this paper we present several ab initio structure determinations of porous materials based on automated diffraction tomography data from single nano crystals. The possibility of collecting data sets of high completeness allows resolving the position of light atoms like oxygen and carbon. The impact of missing information caused by the missing cone effect, preferred orientation or residual beam damage for hybrid materials will be discussed. (C) 2012 Elsevier Inc. All rights reserved.