In attached file, authors have used eq-2 and eq-3 to calculate dislocation density and strain. The formulas look strange and no references are given by the authors.
The paper you attached shows a number of serious flaws. Firstly, the signal to noise of the XRD pattern is extremely bad. Secondly, the FWHM of crystalline peaks over an amorphous background has not been calculated correctly. Finally, the instrumental broadening was not taken into account. The grain sizes calculated with these uncorrected FWHM values led to sizes down to 15 nm!
I'm not sure how that paper got published. In any case, even with useful data the Scherrer formula is untrustworthy, and no one would seriously believe dislocation density and strain values calculated by that method.