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Disorder in crystals

Disorder in crystals. Disorder in crystals. All lattice points are not always the same. Apatite Ca 3 (PO 4 ) 2. Ca 2+. Apatite Ca 3 (PO 4 ) 2. Ca 2+ 0.98 Å. Apatite Ca 3 (PO 4 ) 2. Ca 2+ 0.98 Å. Sr 2+ 1.12 Å. Apatite Ca 3 (PO 4 ) 2. Ca 2+ 0.98 Å.

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Disorder in crystals

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  1. Disorder in crystals

  2. Disorder in crystals All lattice points are not always the same.

  3. Apatite Ca3(PO4)2

  4. Ca2+ Apatite Ca3(PO4)2

  5. Ca2+ 0.98Å Apatite Ca3(PO4)2

  6. Ca2+ 0.98Å Sr2+ 1.12Å Apatite Ca3(PO4)2

  7. Ca2+ 0.98Å Sr2+ 1.12Å Apatite Ca3(PO4)2

  8. Group II Be Mg Ca Sr Ba Ra

  9. Group II Be Mg Ca Sr Ba Ra 2+ in ionic compounds

  10. Group II Be Mg Ca Sr Ba Ra 2+ in ionic compounds 88Sr – 86% of naturally occuring 38

  11. Group II Be Mg Ca Sr Ba Ra 2+ in ionic compounds 88Sr – 86% of naturally occuring 38 90Sr – radioactive isotope product of nuclear weapons testing 38

  12. Apatite Ca3(PO4)2 Ca2+ 0.98Å If Sr2+ replaces Ca2+ consistently, the structure changes. Sr2+ 1.12Å

  13. Apatite Ca3(PO4)2 Ca2+ 0.98Å If Sr2+ replaces Ca2+ consistently, the structure changes. This is not disorder. Sr2+ 1.12Å

  14. Apatite Ca3(PO4)2 Ca2+ 0.98Å If Sr2+ replaces Some Ca2+ randomly, the structure is disordered. Sr2+ 1.12Å

  15. If a crystal contains 90% Ca and 10% Sr, each M2+ site will appear to be Ca/Sr 90/10% based on diffraction data.

  16. Defects in Crystals

  17. Defects in Crystals Disorder implies that all positions are occupied, but the occupation of some sites may not be consistent.

  18. Defects in Crystals A defect is a break in the infinite lattice.

  19. Defects in Crystals A defect is a break in the infinite lattice. Some sites that would normally be occupied in a perfect lattice, are open.

  20. Color center defect - h + Cl- Cl + e-

  21. Color center defect - h + Cl- Cl + e- Cl 0.99 Å Cl- 1.81 Å

  22. The uncharged Cl is not affected by the + charges and is considerably smaller than the Cl-.

  23. The uncharged Cl is not affected by the + charges and is considerably smaller than the Cl-. The Cl can move through, and leave, the lattice.

  24. The uncharged Cl is not affected by the + charges and is considerably smaller than the Cl-. The Cl can move through, and leave, the lattice. The electron can be trapped in the octahedral vacancy left by the Cl-.

  25. Anion missing; replaced by e-.

  26. Anion missing; replaced by e-. The overall lattice is not disturbed.

  27. This does not have to be the same site vacated By the Cl-. Anion missing; replaced by e-.

  28. Anion missing; replaced by e-. Color center defect

  29. Color center defect The presence of e- in a void leads to an electronic transition in the visible range.

  30. In a real (as opposed to a ‘perfect’) Crystal, a small portion of the sites will be unoccupied.

  31. In a real (as opposed to a ‘perfect’) Crystal, a small portion of the sites will be unoccupied. This is called a Shottky defect.

  32. Perfect + -

  33. Real Perfect + -

  34. Real Perfect + - In ionic crystals, charges still must balance.

  35. Shottky Defect

  36. Shottky Defect: a void that does not disturb the structure.

  37. Shottky Defect in metal.

  38. Other defects may alter the lattice.

  39. + - Interstitial site:

  40. + - Interstitial site: position between ions or atoms which can be occupied by another ion or atom.

  41. + - Interstitial site: position between ions or atoms which can be occupied by another ion or atom.

  42. + - Move ion from normal site to interstitial site.

  43. Frenkel defect: lattice is distorted when an ion is moved to an interstitial site.

  44. Defects tend to be dynamic.

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