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Real space crystallography of a complex metallic alloy: HAADF STEM of o-Al4(Cr,Fe)

 Roberto Gaspari (1a,2), Rolf Erni (3), Yadira Arroyo (3), Magdalena Parlinska-Wojtan (3), Julia Dshemuchadse (4), Carlo A. Pignedoli (1a), Daniele Passerone (1a), Patrik Schmutz (1b), Alessandra Beni (1b,*)


(1a) nanotech@surfaces and (1b) Joining Technology and Corrosion Laboratories, Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, Duebendorf, 8600, Switzerland.

(2) D3- Computation, Italian Institute of Technology, via Morego 30, Genova, 16163, Italy.

(3) Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, Duebendorf, 8600, Switzerland.

(4) Laboratory of Crystallography, Department of Materials, ETH Zurich, Wolfgang-Pauli Strasse 10, Zurich, 8093, Switzerland.

 

* alessandra.beni@empa.ch

  

HAADF STEM (High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy) is performed along the low index zone axes of the o-Al4(Cr,Fe) complex metallic alloy to obtain a real space representation of the crystal structure and to elucidate the material’s inherent structural disorder. By comparing experiments to multislice STEM simulations, the model previously suggested by X-ray diffraction has been further refined, obtaining a new set of positions and occupations for the transition metal atoms and suggesting Pmnb as new space group for the o-Al4(Cr,Fe) phase.


  
 

DOI link: doi:10.1107/S1600576714008656 

Comparison between the experimental STEM images and the multislice STEM simulations along the low index zone axis; (c) Simulation of the previous structural model. The relevant symmetry elements for the Pmnb space group are superimposed in the simulated images.
Comparison between the experimental STEM images and the multislice STEM simulations along the low index zone axis; (c) Simulation of the previous structural model. The relevant symmetry elements for the Pmnb space group are superimposed in the simulated images.