x-ray crystallography,bragg's law,different x-ray diffraction technique,laue photographic method,bragg's x-ray spectrometer method,rotating crystal method,x-ray powder technique,type of crystal ,application of x-ray diffraction

X-ray crystallography,brag law, bragg's law, bragg's specrtometer method, braggs law, brags law, crystallography, different x-ray diffraction technique, diffrection technique, laue method, laue photographic method, powder crystal method, powder method, r, rotating crystal method, type of crystal, x ray crystallograph, x- ray crystallography, x-ray, x-ray crystallography, x-ray crystallography application

1. Presented by: Pratik Siddhapura M.Pharm 1 st Year Sem- 1 Department of pharmaceutics X-RAY CRYSTALLOGRAPHY

2. Content X- ray diffraction Bragg’s law Different X-ray diffraction techniques Laue photographic method Bragg’s X-ray spectrometer method Rotating crystal technique X-ray powder technique Type of crystal Application of x-ray diffraction

3. X-ray crystallography works based on X-ray diffraction principle: It means that scattering of x-ray by crystal. X-ray diffraction is based on constructive interference of monochromatic X rays and crystalline sample. X- ray diffraction

4. Bragg’s Law Diffraction occurs only when Bragg’s Law is satisfied. Bragg law identifies the angles of the incident radiation relative to the lattice planes for which diffraction peaks occurs. Bragg derived the condition for constructive interference of the X-rays scattered from a set of parallel lattice planes. When the X-rays strike a layer of a crystal, some of them will be reflected. These two x-ray beams travel slightly different distances. Connecting the two beams with perpendicular lines shows the difference between the top and the bottom beams. For a crystalline solid, the waves are scattered from lattice planes separated by the inter planar distance d . When the scattered waves interfere constructively, they remain in phase since the difference between the path lengths of the two waves is equal to an integer multiple of the wavelength. The path difference between two waves undergoing interference is given by 2 d sin θ , where θ is the scattering angle.

5. crystal

6. According to the 2 θ deviation, the phase shift causes constructive (left figure) or destructive (right figure) interferences.

7. The length AB is the same as BC so the total distance traveled by the bottom wave is expressed by: AB= d sinθ BC = d sinθ AB+ BC= 2d sinθ n λ = 2d sinθ Constructive interference of the radiation from successive planes occurs when the path difference is an integral number of wave lengths. This is the Bragg Law.

8. 1 .Laue photographic method Transmission method In this method the crystal is held stationary in a beam of x-rays , after passing through the crystal is diffracted and is recorded on a Photographic plate . Laue pattern can be used to orient crystals for solid Sta te experiments.

9. 1 .Laue photographic method Back reflection method The film is placed between the x-ray source and the crystal. The beams which are diffracted in backward direction are recorded.

10. 2.Bragg X-ray spectrometer method

11. Construction:- Bragg's Spectrometer consists of a collimator containing two slits S 1 and S 2 made up of lead, through which X-ray is passed. A turn table is situated in-front of the collimator on which crystal is placed. Ionization chamber collects the reflected X-ray Procedure:- A fine beam of a monochromatic X-ray is made to fall on the crystal. The crystal reflects the X-rays which are collected by the ionization chamber. Turn table is rotated till a sharp increase in the intensity is detected. The sudden increase in intensity suggests that Bragg's Law is satisfied at the given angle θ. Then the inter-planar spacing can be determined by using Bragg's Law nλ = 2d.sinθ

12. 3. Rotating crystal method The X- rays are generated in the X-ray tube and then the beam is made by monochromator. The beam is allowed to pass through collimating system which permits a parallel X-rays. Then the X –ray beam is made to fall on crystal which is mounted on a rotating shaft. When x-ray strike on crystal plane, it will produce a spot on photographic film.

13. X – ray diffraction pattern

14. 4. Powder crystal method When an X-ray is shined on a crystal, it diffracts in a pattern characteristic of the structure. In powder X-ray diffraction, the diffraction pattern is obtained from a powder of the material. Powder diffraction is often easier and more convenient than single crystal diffraction since it does not require individual crystals be made. Powder X-ray diffraction (XRD) also obtains a diffraction pattern for the bulk material of a crystalline solid, rather than of a single crystal.

15. Powder crystal method

16. Type of crystal

17. Application X-ray powder diffraction is most widely used for the identification of unknown crystalline materials (e.g. minerals, inorganic compounds). characterization of crystalline materials identification of fine-grained minerals such as clays and mixed layer clays that are difficult to determine optically determination of unit cell dimensions

18. To identify crystalline phases and orientation To determine structural properties: To measure thickness of thin films and multi-layers To determine atomic arrangement measurement of sample purity

19. Particle size determination Determination of Cis - Trans isomerism It is used to assess the weathering and degradation of natural and synthetic , minerals. Tooth enamel and dentine have been examined by xrd.

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