Hi, researchers,
I am studying a complicated structure and its electron diffraction has some confusing features.
There are often weak spots emerging in the SAED patterns and some articles think it is the superlattice reflections. But it seems to come from double diffraction, especially in the Fig.2 I attached.
So, any could help me to distinguish the double diffraction and superlattice reflection from a SAED pattern?
Thanks very much.
I don't know the exact meaning for double diffraction, if you mean from twin crystals then they should hav the same diffraction angles or the same pattern as it's from the same single crystal
while super lattice means the diffraction is from a crystal have two unit cell arrangements the first is the original and the second is its multiplication, in this case there will be two sets of diffraction angles each belongs to its related structure but bot of them will saticefy lattice parameter for both structures through their related parameters
for more information try to see the article
"A Triclinic super lattice structure for the bended sphalerite unit cell of the compound Cu2GeS3"
M. S. Omar
Arab gulf J. Scient. Res., 15, (2), 353, (1997)
Dear Sir,
the way you analyzed the diffraction pattern in the first image seems quite confusing. Please note that in a diffraction experiment the Bravais (!) lattice
of the reciprocal space is probed. The lattice that is formed by the small hexagons as well the lattice formed by the large hexagons is not a Bravais lattice.
Sincerely, FM
The simplest and common way in TEM to find out if the reflections in ED pattern come from double diffraction is to tilt a TEM specimen by several degree out of zone axis. If the intensity of assumed double diffraction spots becomes very weak or even disappears at a certain tilt angle, than the reflections are due to the double diffraction.
Thanks for Omar's advice, I will read carefully the paper you recommend.
Thanks for Frank's answer, but Fig.1 is not my analysis. It is a screenshot from a paper in Nat. Mater. I also is confused with this result.
Thank you, Andriy Lotnyk. Whether you can give me some hints to distinguish these two kinds of ED spots just from the features in patterns?
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