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A new electron diffraction approach for structure refinement applied to Ca 3 Mn 2 O 7
Author(s) -
Beanland R.,
Smith K.,
Vaněk P.,
Zhang H.,
Hubert A.,
Evans K.,
Römer R. A.,
Kamba S.
Publication year - 2021
Publication title -
acta crystallographica section a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.742
H-Index - 83
ISSN - 2053-2733
DOI - 10.1107/s2053273321001546
Subject(s) - octahedron , electron diffraction , diffraction , electron , perpendicular , crystallography , phase (matter) , atom (system on chip) , materials science , crystal structure , chemistry , molecular physics , atomic physics , physics , optics , geometry , mathematics , organic chemistry , quantum mechanics , computer science , embedded system
The digital large‐angle convergent‐beam electron diffraction (D‐LACBED) technique is applied to Ca 3 Mn 2 O 7 for a range of temperatures. Bloch‐wave simulations are used to examine the effects that changes in different parameters have on the intensity in D‐LACBED patterns, and atomic coordinates, thermal atomic displacement parameters and apparent occupancy are refined to achieve a good fit between simulation and experiment. The sensitivity of the technique to subtle changes in structure is demonstrated. Refined structures are in good agreement with previous determinations of Ca 3 Mn 2 O 7 and show the decay of anti‐phase oxygen octahedral tilts perpendicular to the c axis of the A 2 1 am unit cell with increasing temperature, as well as the robustness of oxygen octahedral tilts about the c axis up to ∼400°C. The technique samples only the zero‐order Laue zone and is therefore insensitive to atom displacements along the electron‐beam direction. For this reason it is not possible to distinguish between in‐phase and anti‐phase oxygen octahedral tilting about the c axis using the [110] data collected in this study.