I am not able to understand why the data we get from single crystal XRD is 3D where as from powder XRD is 1D.?
How did we define it as 1D and 3D.?
Answer from Breuer is giving almost a compleye explanation to the question
for single crystal only single spot for each crystaline plain will obtained while for powder there are als one spot for each single crystal but there are thousands and more of them producing a continuous line form in a circle shape
Hi Sai,
Just adding to Thomas Breuers reply.
You can imagine a powder sample as a random distribution of a very large number of very small single crystals. This means small crystals oriented in all possible directions. Bragg reflections from the random orientations will form concentric cones (Laue cones). These cones should project into a 2D detector surface (many modern PXRD machines have this) as concentric rings (cross sections of the Laue cones).
If you imagine a radial line from centre to the outermost ring as x -axis, and plot the diffraction intensity of each ring as y-axis you get a graph- this is your powder diffraction pattern. It is 1D- because it has intensity-information for just Bragg angle (theta).
When X-rays hit a single crystal- you can imagine that it acts like a chamber with mirrors oriented in different directions (NB: each imaginary mirror is a set of miller planes). As a result you get Bragg reflections which are directionally resolved. The spots you observe on a detector plate might collectively look like a 2D pattern but these have the angular information on the exact crystal orientation (not just theta) using which you an get the 3D metric geometry of your crystal unit cell (and the molecular structure using a more complex analysis of the intensities). In that sense , it is a 3D pattern.
Cheers.
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