Powder diffraction peak shape information

The analysis of XRPD patterns is an important tool studying the crystallographic structure and composition of powder compounds including the possibility to study deviation from ideal crystallinity, i.e. defects. Looking at an X-ray powder diffractogram the peak position reflects the crystallographic symmetry (unit cell size and shape) while the peak intensity is related to the unit cell composition (atomic positions). The shape of diffraction lines is related to defects , i.e. deviation from the ideal crystallinity finite crystallite size and strain lead to broadening of the XRPD lines so that the analysis of diffraction line shape may supply information about sample microstructure and defects distribution at the atomic level. 

Figure 1. Schematic of an experimental setnp for high-pressure X-ray diffraction (XRD) experiments on nanocrystals nnder pressure of tens of GPa (1 GigaPascal s 10,000 atmospheres). Nanociystal powder is dissolved in a pressme medinm and placed between two opposing diamonds, which are clear to X-rays and visible absorption. The pressme is applied by bringing the diamond closer together, and measmed nsing pieces of ruby chips placed inside the pressme cell. The XRD diffraction peaks are Debye-Scherrer broadened by the finite size of the particles, yielding information on the shape and size of the nanocrystals before and after the transition, snch as shown in Figure 3.

---