Comparison of LiF and NiO crystallographic structure using XRD

\newline Using x-ray diffraction (XRD), the crystallographic structures of LiF and NiO powders and single crystals were compared. ~Two types of scans were taken: $\omega $-2$\theta $ scans were taken for both the powders and single crystals, and $\omega $ (rocking curve) scans were taken for the single crystals. ~~LiF is of the face-centered cubic rock salt structure, whereas NiO contracts along the [111] direction producing a trigonal (hexagonal) crystal structure. ~Therefore, the cubic (222) peak splits in bulk NiO into hexagonal (006) and (202) peaks. ~From the $\omega $-2$\theta $ NiO powder scans, no splitting of the c(222) peak is observed because the NiO is a nano-powder, preferring high symmetry orientations. ~The $\omega $-2$\theta $ peaks are broader in NiO powder because the grain size is smaller in the NiO than in LiF powders. ~The rocking curve scans of the c(222) peaks show that the single crystals have multiple domains.