Types of Crystals and Application of X-ray Diffraction

Definition to x-ray crystallography and x-ray diffraction. Types of crystal and Application of X-ray diffraction.

1. Modern Pharmaceutical Analytical Techniques Types of crystals & Applications of x-ray diffraction By, Rajeshwari . V M.Pharm 1 st year KMCH College of Pharmacy 1

2. Contents X-ray crystallography X-ray Diffraction Types of crystal Applications of X-ray diffraction 2

3. 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 . 3

4. X-ray diffraction X - ray diffraction , 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 . 4

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6. Types of Crystal 6

7. C rystal Lattice A crystal lattice is a 3-D arrangement of unit cells. Unit cell is the smallest unit of a crystal, by stacking identical unit cells, the entire lattice can be constructed. A crystal’s unit cell dimensions are defined by six numbers, the lengths of the 3 axes, a, b, and c, and the three inter axial angles, α, β and γ. 7

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10. Bravais Lattice refers to the 14 different 3-dimensional configurations into which atoms can be arranged in crystals. 10

11. THE 7 CRYSTAL SYSTEMS 1. Cubic Crystals a = b= c α = β = γ= 90 º Ex: - NaCl , KCl Pyrite Cube   11

12. 2. Tetragonal Crystals a = b ≠ c α = β = γ = 90 º Ex:-TiO2 Zircon   12

13. 3. Hexagonal Crystals a = b ≠ c α= β = 90 º γ= 120 º Ex:-Mg, Zn, ZnO Corundum 13

14. 4. Orthorhombic Crystals a≠ b≠ c α= β= γ= 90 º Ex:-BaSO4, KNO3 Topaz 14

15. 5. Rhombohedral Crystals a = b = c α , β , γ ≠ 90 º Ex:-Graphite Tourmaline 15

16. 6. Monoclinic Crystals a ≠ b ≠ c α≠ 90 º, β, γ = 90 º Eg -Kunzite 16

17. 7. Triclinic Crystals a ≠b ≠ c α ≠β≠γ not equal to 90º Eg -Amazonite 17

18. Application of X-ray diffraction 18

19. 1.Structure of crystals X-ray Diffraction Method is non-destructive and gives information on the molecular structure of the sample. Comparing diffraction patterns from crystal of unknown composition with patterns from crystal of known compounds permits the identification of unknown crystalline compound. This method can also be used to distinguish between a mixture of crystals . 19

20. 2. Polymer characterization Determine degree of crystallinity . Non-crystalline portion scatters x-ray beam to give a continuous background(amorphous materials) Crystalline portion causes diffraction lines that are not continuous(crystalline materials ).   20

21. 3. State of anneal in metals A property of metals than can be determined by X-ray diffraction is the state of anneal. Well-annealed metals are in well-ordered crystal form and give sharp diffraction lines. It is occasionally necessary to check moving parts for metal fatigue , such as airplane wings . This check can be done by x-ray diffraction without removing the part from its position and without weakening it in the process of testing 21

22. 4.Particle size determination Spot counting method Broadening Of Diffraction Lines Low-Angle Scattering 22

23. A. Spot counting method This method is used for determining size of particles larger than 5 microns. v=V. δθ . cosθ /2n Where, V =volume of individual crystallite V =total volume irradiated n =no. of spots in diffraction ring at a Bragg angle of θ δθ =divergence of x-ray beam . 23

24. B. Broadening Of Diffraction Lines Crystallites smaller than 120nm create broadening of diffraction peaks. This peak broadening can be used to quantify the average crystallite size of nano particles Using the scherrer’s equation. 24

25. C. Low-Angle Scattering From the Bragg relation, nλ =2d sinθ it follows that if one desire to have information about large structural features ( i.e.,large d values),attention should be focussed on small scattering angles,2θ to get better resolution. 25

26. 5. Diffraction methods to complexes   A. Determination of Cis -Trans: Isomerism-X-ray diffraction study has been used to make the distinction between cis and trans isomers of a complex. B. Determination of Linkage Isomerism : By X- ray studies, it becomes possible to identify linkage isomers of complexes.  26

27. References Instrumental Analysis by James W Robinson, Eileen M. Skelly Frame George M. Frame II. 3 rd edition. Journal - x  Ray crystallography by MS Smyth and JHJ Martin. Pharmaceutical Analysis – A textbook for pharmacy students and Pharmaceutical chemists edited by David G Watson. 27

28. Thank you… 28