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Solving difficult structures with electron diffraction.

Zuo JM, Rouviére JL - IUCrJ (2015)

Bottom Line: Precession electron diffraction has solved a long-standing challenge in electron diffraction.Further progress promises a general technique for structure determination of difficult crystals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, University of Illinois , Urbana, IL 61801, USA ; Seitz Materials Research Laboratory, University of Illinois , Urbana, IL 61801, USA ; CEA/INAC/SP2M/LEMMA , 19 rue des Martyrs, Grenoble, 38 054, France.

ABSTRACT
Precession electron diffraction has solved a long-standing challenge in electron diffraction. Further progress promises a general technique for structure determination of difficult crystals.

No MeSH data available.


CBED patterns recorded using 200 kV electrons from Si along [001] (left) without and (right) with precession (precession angle 0.6°), respectively.
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fig1: CBED patterns recorded using 200 kV electrons from Si along [001] (left) without and (right) with precession (precession angle 0.6°), respectively.

Mentions: In the topical review by Midgley and Eggeman (Midgley & Eggeman, 2015 ▶), the authors describe the remarkable progress made in an alternative approach to electron structure solution, precession electron diffraction (PED), a technique discovered 20 years ago by Vincent & Midgley (1994 ▶). In PED, the incident electron beam rotates around a crystal direction, keeping a constant angle – the ‘precession angle’ – with this crystal direction. To compensate for the motion of diffracted beams as the incident beam rotates, the outgoing beams are deflected back (Fig. 1 ▶ in Midgley & Eggeman, 2015 ▶), similar to the double rocking technique for the recording of large-angle CBED patterns (Eades, 1980 ▶). By recording electron diffraction patterns with the incident electron beam in precession, PED is able to provide the integrated electron diffraction intensity across the Bragg condition for many reflections. The use of such intensities for structure solution in numerous test structures has shown surprising robustness against crystal thickness variations and small crystal misorientations, which could have a dramatic effect on electron diffraction intensities recorded using conventional techniques (see Fig. 1 ▶). Using PED intensities, crystal structures can be solved by a combination of phasing and structure refinement, where the R factor can be reduced to less than 10% by further including dynamic effects (Palatinus et al., 2013 ▶; Jacob et al., 2013 ▶).


Solving difficult structures with electron diffraction.

Zuo JM, Rouviére JL - IUCrJ (2015)

CBED patterns recorded using 200 kV electrons from Si along [001] (left) without and (right) with precession (precession angle 0.6°), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4285875&req=5

fig1: CBED patterns recorded using 200 kV electrons from Si along [001] (left) without and (right) with precession (precession angle 0.6°), respectively.
Mentions: In the topical review by Midgley and Eggeman (Midgley & Eggeman, 2015 ▶), the authors describe the remarkable progress made in an alternative approach to electron structure solution, precession electron diffraction (PED), a technique discovered 20 years ago by Vincent & Midgley (1994 ▶). In PED, the incident electron beam rotates around a crystal direction, keeping a constant angle – the ‘precession angle’ – with this crystal direction. To compensate for the motion of diffracted beams as the incident beam rotates, the outgoing beams are deflected back (Fig. 1 ▶ in Midgley & Eggeman, 2015 ▶), similar to the double rocking technique for the recording of large-angle CBED patterns (Eades, 1980 ▶). By recording electron diffraction patterns with the incident electron beam in precession, PED is able to provide the integrated electron diffraction intensity across the Bragg condition for many reflections. The use of such intensities for structure solution in numerous test structures has shown surprising robustness against crystal thickness variations and small crystal misorientations, which could have a dramatic effect on electron diffraction intensities recorded using conventional techniques (see Fig. 1 ▶). Using PED intensities, crystal structures can be solved by a combination of phasing and structure refinement, where the R factor can be reduced to less than 10% by further including dynamic effects (Palatinus et al., 2013 ▶; Jacob et al., 2013 ▶).

Bottom Line: Precession electron diffraction has solved a long-standing challenge in electron diffraction.Further progress promises a general technique for structure determination of difficult crystals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, University of Illinois , Urbana, IL 61801, USA ; Seitz Materials Research Laboratory, University of Illinois , Urbana, IL 61801, USA ; CEA/INAC/SP2M/LEMMA , 19 rue des Martyrs, Grenoble, 38 054, France.

ABSTRACT
Precession electron diffraction has solved a long-standing challenge in electron diffraction. Further progress promises a general technique for structure determination of difficult crystals.

No MeSH data available.