X ray diffraction method

X RAY DIFFRACTION

1. PRESENTED BY : ANANT NAG ID : 17BPH005 BATCH : 17-2021 Semester 8 th (4 TH YEAR) X-RAY DIFFRACTION METHOD

2. DEFINITION X-ray diffraction , is a phenomenon in which the atoms of a  crystal , by virtue of their uniform spacing, cause an interference pattern of the waves present in an incident beam of X rays. The atomic planes of the crystal act on the X rays in exactly the same manner as does a uniformly ruled grating on a beam of light.

3. X-RAY DIFFRACTION IS USE FOR

4. The incoming beam (coming from upper left) causes each scatterer to re-radiate a small portion of its intensity as a spherical wave. If scatterers are arranged symmetrically with a separation d, these spherical waves will be in sync (add constructively) only in directions where their path-length difference 2d sin θ equals an integer multiple of the  wavelength  λ. In that case, part of the incoming beam is deflected by an angle 2θ, producing a reflection spot in the  diffraction pattern

5. ORIGIN OF X-RAY

6. How X-RAY DIFFRACTION WORK?

7. BASIC ASPECTS OF CRYSTALS In a single- crystal X - ray  diffraction measurement, a  crystal  is mounted on a goniometer . The goniometer is used to position the  crystal  at selected orientations. The  crystal  is illuminated with a finely focused monochromatic beam of  X - rays , producing a diffraction pattern of regularly spaced spots known as reflections. The two-dimensional images taken at different orientations are converted into a three-dimensional model of the density of electrons within the crystal using the mathematical method of  Fourier transforms , combined with chemical data known for the sample. Poor resolution (fuzziness) or even errors may result if the crystals are too small, or not uniform enough in their internal makeup.

8. X-RAY CRYSTALLOGRAPHY X-ray crystallography  ( XRC ) is the experimental science determining the atomic and molecular structure of a  crystal , in which the crystalline structure causes a beam of incident  X-rays  to  diffract  into many specific directions. By measuring the angles and intensities of these diffracted beams, a  crystallographer  can produce a three-dimensional picture of the density of  electrons  within the crystal. From this  electron density , the mean positions of the atoms in the crystal can be determined, as well as their  chemical bonds , their  crystallographic disorder , and various other information. Since many materials can form crystals—such as  salts ,  metals ,  minerals ,  semiconductors , as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields.

9. ROTATING CRYSTAL TECHNIQUE The  rotation method  is the most common  method  to determine steady state  crystal  structures. The orientation of the  rotation  axis and the  rotation  range can be chosen to select a subset of diffraction peaks fulfilling the Bragg condition Δk = k − k = Hhkl ( r,φ )

10. SINGLE CRYSTAL DIFFRACTION Single - crystal  X-ray Diffraction is a non-destructive analytical technique which provides detailed information about the internal lattice of  crystalline  substances, including unit cell dimensions, bond-lengths, bond-angles, and details of site-ordering.

11. POWDER DIFFRACTION X-ray powder diffraction (XRD) is a rapid analytical technique primarily used for phase identification of a crystalline material and can provide information on unit cell dimensions. The analyzed material is finely ground, homogenized, and average bulk composition is determined.

12. STRUCTURAL ELUCIDATION

13. APPLICATIONS

14. REFERENCES "Resonant X-ray Scattering | Shen Laboratory" . arpes.stanford.edu. Retrieved 2019-07-10. ( https://en.wikipedia.org/wiki/X-ray_crystallography ) A Powerpoint presentation on use of XRD in Soil Science  (PowerPoint 1.6MB Sep7 07) by Melody Bergeron,  Image and Chemical Analysis Laboratory  at Montana State University. ( https://www.xos.com/XRD ) Vinita  Vishwakarma ,  Sudha   Uthaman , in  Smart Nanoconcretes and Cement-Based Materials , 2020 ( https://www.jove.com/v/10446/x-ray-diffraction ) Jeff Dahl ( https://www.britannica.com/science/X-ray-diffraction ) Brady, John B., and Boardman, Shelby J., 1995, Introducing Mineralogy Students to X-ray Diffraction Through Optical Diffraction Experiments Using Lasers. Jour. Geol. Education, v. 43 #5, 471-476. ( https://serc.carleton.edu/research_education/geochemsheets/techniques/XRD.html )

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