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SUMMARY:Structure determination by electron crystallography: a powerful co
 mplement to conventional methods for structure elucidation - Tom Willhamma
 r\, Department of Materials and Environmental Chemistry\, Stockholm Univer
 sity\, Stockholm SE−106 91\, Sweden
DTSTART:20170424T103000Z
DTEND:20170424T113000Z
UID:TALK72068@talks.cam.ac.uk
CONTACT:Duncan Johnstone
DESCRIPTION:Knowledge about the atomic structure of new materials is essen
 tial in order to understand its properties\, improve its design and develo
 p applications. Modern materials with increasing complexity increases the 
 demands on the structural characterization.\n\nRecent developments now mak
 es it possible to obtain 3D single crystal electron diffraction data from 
 crystals down towards the nanometer range. This method has been applied fo
 r the structure determination of a large number of new materials\, includi
 ng a significant number of porous materials such as zeolites and Metal-org
 anic Frameworks\, where the crystals has been too small for structure dete
 rmination by conventional methods. Electron microscopy also provides the o
 pportunity of image formation\, enabling studies of atomic arrangements at
  the local scale. This is of importance\, especially for materials contain
 ing structural disorders. The combination of these two advantages provides
  unique tools for studies of materials with complex structures.\n\nOne exa
 mple is the zeolite ITQ-39\, exhibiting a PXRD pattern with a small number
  of broad peaks. The crystals are needle like\, with a cross section of on
 ly ~30 nm. By combining 3D electron diffraction data with high resolution 
 transmission electron microscopy (HRTEM) images\, the structure of ITQ-39 
 could be determined.[1] The structure turned out to possess severe disorde
 rs including a random intergrowth of three different polytypes and in addi
 tion twinning. In a recent study the 3D electron diffraction method was co
 mplemented by real space electron tomography at the atomic scale for the s
 tructural characterization of a luminescent CuTe. The average atomic struc
 ture was determined from the electron diffraction data and subsequently th
 e distribution of Cu vacancies in the material could be studied using elec
 tron tomography.[2]\n\nReferences:\n[1] Willhammar\, Zou\, Corma et. al.\,
  Nature Chem. 4 188 (2012)\n[2] Willhammar\, Liz-Marzán\, Bals\, van Tend
 eloo et.al. Nature Comms. 8 14925 (2017)
LOCATION:Goldsmiths 1\, Lecture room\, Dept. of Materials Science and Meta
 llurgy
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