《XRD_》.pdf

Department of Chemical Biological Engineering Basics of X-Ray Diffraction Ziyou Zhou Department of Chemical Biological Engineering X-ray Diffraction (XRD)   1.0 Principle of XRD   2.0 Instrument   3.0 Applications of XRD   4.0 Experiments and Results Department of Chemical Biological Engineering Principle of XRD Department of Chemical Biological Engineering Crystalline materials are characterized by the orderly periodic arrangements of atoms The (200) planes The (220) planes of atoms in NaCl of atoms in NaCl   The unit cell is the basic repeating unit that defines a crystal.   Parallel planes of atoms intersecting the unit cell are used to define directions and distances in the crystal. –  These crystallographic planes are identified by Miller indices. Department of Chemical Biological Engineering The atoms in a crystal are a periodic array of coherent scatterers and thus can diffract light   Diffraction occurs when each object in a periodic array scatters radiation coherently, producing concerted constructive interference at specific angles.   The electrons in an atom coherently scatter light. –  The electrons interact with the oscillating electric field of the light wave.   Atoms in a crystal form a periodic array of coherent scatterers. –  The wavelength of X rays are similar to the distance between atoms. –  Diffraction from different planes of atoms produces a diffraction pattern, which contains information about the atomic arrangement within the crystal   X Rays are also reflected, scattered incoherently, absorbed, refracted, and transmitted when they interact with matter.