The dislocation density is a measure of the number of dislocations in a unit volume of a crystalline material i.e. the length of dislocation lines per unit volume of the crystal (m/m3) Edge dislocation Screw dislocation Dislocations distort a crystal lattice, causing elastic stress around the dislocation line, & hence strain energy. For ultimate strength, dislocations are to be eliminated.
In this video, I have discussed the nature of dislocation density and how to calculate the dislocation density from XRD using origin. In the case you want to further ask about it, please do comment on the specific video, I'll respond to it shortly. I have provided the practice as well as calculations files here. Thanks
https://youtu.be/WyvwytYYSK8
Dear Shahid Ali ,
thanks for the tutorial on calculating the dislocation density via origin.
The key of that calculation is the Williamsen Smallman relation delta=1/D². This relation is simply thrown into your tutorial.
Due to the fact that the term 'dislocation density' is one of two main phrases of the title of your video I would like to have from the viewers prespective a) a short explanation on how this relation is derived, or b) a simple explanation on why there is a D² dependence. It is quite clear that a length (of dislocation) divided by a volume is an inverse area; but why it is just 1/D² without any scaling factor from the physics point of view.
In addition a short discussion on the contraints making this relation valid, should not be omitted.
Apart from that the extraction of D from the XRD pattern via Scherrer or Williamsen-Hall relations using origin is straightforward handling a software and the presentation is ok.
Gerhard Martens Your suggestions/input are well taken. I'll include them in the forthcoming video on the same topic. Thanks
Shahid Ali
thanks for feedback.
I am eager to the the upgraded one....
Variations in the height of the specimen in its holder, whether increasing or decreasing, cause XRD peaks to change from their original location.
Important and useful pathways are connected to the XRD Curve:
Scherrer’s equation:
Particle Size, D = (0.9 x λ)/ (d cosθ)
λ = 1.54060 Å (in the case of CuKa1) so, 0.9 x λ = 1.38654
Θ = 2θ/2 (in the example = 20/2)
d = the full width at half maximum intensity of the peak (in Rad) – you can calculate it using Origin software.
To convert from angle to rad
Rad = (22 x angle) / (7 x 180) = angle x 0.01746
Example: if d = 0.5 angle (θ)
= (22 x 0.5)/ (7x 180) = 0.00873 rad
Then
Delta=1/D^2
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