Assessing the dislocation density in CdSe nanocrystals from XRD peak profile analysis (XDPPA) assisted by first principles method

Abstract

Nanocrystalline CdSe has been synthesized via a wet chemical technique followed by characterized using XRD and HRTEM. Classical (CWH) and modified Williamson Hall (MWH) techniques have been used for the determination of microstructures based on the X-ray diffraction peak profile analysis (XDPPA). Rietveld refinement of the experimental XRD pattern provides the refined full width at half maximum (FWHM) of CdSe nanocrystals. Here, the output structural information as obtained from the Rietveld refinement method has been fed into the Quantum Espresso (QE) code for the determination of elastic constants of CdSe using the first principles method. Both the FWHM and elastic constants are used in CWH and MWH analysis. Since the MWH method considers the strain anisotropy of the crystals, it can provide a better fit than the CWH method. In addition to this, the MWH method has been used to find out the dislocations character present in the CdSe nanocrystals. Dislocations are important because these are responsible for inducing strain in the nanocrystals.