Authors: P. Moeck, R. Bjorge and P. Fraundorf
Affilation: Portland State University, United States
Pages: 93 - 96
Keywords: nanocrystal characterization, TEM, STEM, open-access crystallographic databases
It is well known that many nanocrystals can not be identified from their powder X-ray diffraction pattern as it is customary for collections of micrometer sized crystals. The crystallographic phase and shape of nanocrystals can, however, be determined by transmission electron microscopy (TEM) at lattice and/or atomic resolution combined with tools for image-based nanocrystallography. This talk discusses two such tools: lattice-fringe fingerprinting in two dimensions (2D) for the identification of unknown nanocrystal phases and tilt protocol applications in three dimensions (3D) for the determination of the shape of nanocrystals. Although feasible in contemporary TEMs, image-based nanocrystallography is much more viable in aberration corrected microscopes. The Crystallography Open Database (COD, http://crystallography.net), its mainly inorganic subset (which serves the TEM community) http://nanocrystallography.research.pdx.edu/cif-searchable/cod.php (TEM-COD), and the Nano-Crystallography Database http://nanocrystallography.research.pdx.edu/cif-searchable/ncd.php are discussed because the whole lattice-fringe fingerprinting concept is only viable if there are comprehensive databases to support the identification of an unknown nanocrystal phase. While and the COD contains the atomic coordinates, space group, lattice parameters, and other crystallographic information for more than 50,000 compounds, the TEM-COD and NCD provide, in addition, interactive 3D structure visualizations and theoretical 2D lattice-fringe fingerprint plots for about 10,000 compounds.