xrd射线衍射分析方法.doc

XRD APPLICATION NO Pair distribution function analysis Total scattering experim using high-energy X-ray a laboratory system Introduction Recent years have shown an increased interest in the study of nanocrystalline materials due to their speci?c properties for application in e.g. semiconductors, pharmaceuticals and polymers. Structural information about these materials is present as broad, not well de?ned features in a diffractogram. Analysis of nanomaterials therefore requires a total scattering approach, including both Bragg peaks and diffuse scattering. One of the most promising analytical methods used is atomic pair distribution function (PDF) analysis. Originally, this method was used to study primarily amorphous and highly disordered materials. More recently, it has been used for the analysis of nanostructured materials. Since the method requires short wavelengths to obtain high resolution in real space (well de?ned interatomic distances), often the measurements are performed at synchrotron facilities, making use of both the high photon energies and the high photon ?ux that these facilities offer. We have investigated the possibility to apply the pair distribution technique on an in-house system, using Ag or Mo Kα radiation. This application note describes typical results on nanocrystals, liquids and amorphous materials. (a) (b) 0 1 2 3 4 5 6 r [?] Schematic representation of the construction of the atomic pair distribution function from a square array of atoms [2]. The colored circles (a) indicate the distance from a central atom where a neighboring atom can be found. The arrows indicate the corresponding peaks in the pair distribution function. Analyzing powder diffraction data of nanocrystalline and amorphous materials using the atomic pair distribution function (PDF) method provides useful information about the long- and short-range ordering of the atoms in the materials. We have developed the application of PDF analysis on a standard laboratory system