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Peretemuan 1<br />PENDAHULUAN FISIKA ZAT PADAT<br />IwanSugihartono, M.Si<br />JurusanFisika FMIPA<br />UniversitasNegeri ...
Crystals<br />06/01/2011<br />©  2010 Universitas Negeri Jakarta   |  www.unj.ac.id                      |<br />2<br /><ul...
   unit cells
   symmetry
   lattices
Diffraction
   how and why - derivation
Some important crystal structures and properties
close packed structures
   octahedral and tetrahedral holes
   basic structures
ferroelectricity</li></li></ul><li>Objectives<br />By the end of this section you should:<br />be able to identify a unit ...
Why Solids?<br />most elements solid at room temperature<br />	atoms in ~fixed position<br />“simple” case - crystalline...
Crystals are everywhere!<br />5<br />06/01/2011<br />©  2010 Universitas Negeri Jakarta   |  www.unj.ac.id                ...
More crystals<br />6<br />06/01/2011<br />©  2010 Universitas Negeri Jakarta   |  www.unj.ac.id                      |<br />
Early ideas<br />Crystals are solid - but solids are not necessarily crystalline<br />Crystals have symmetry (Kepler) and ...
Group discussion<br />8<br />Kepler wondered why snowflakes have 6 corners, never 5 or 7.  By considering the packing of p...
Definitions1. The unit cell<br />“The smallest repeat unit of a crystal structure, in 3D, which shows the full symmetry of...
  3 angles - , , </li></ul>06/01/2011<br />©  2010 Universitas Negeri Jakarta   |  www.unj.ac.id                      |...
 Seven unit cell shapes<br /><ul><li>Cubic		a=b=c		===90°
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Pend Fisika Zat Padat (1) crystal

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Pend Fisika Zat Padat (1) crystal

  1. 1. Peretemuan 1<br />PENDAHULUAN FISIKA ZAT PADAT<br />IwanSugihartono, M.Si<br />JurusanFisika FMIPA<br />UniversitasNegeri Jakarta<br />1<br />
  2. 2. Crystals<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />2<br /><ul><li>Crystal structure basics
  3. 3. unit cells
  4. 4. symmetry
  5. 5. lattices
  6. 6. Diffraction
  7. 7. how and why - derivation
  8. 8. Some important crystal structures and properties
  9. 9. close packed structures
  10. 10. octahedral and tetrahedral holes
  11. 11. basic structures
  12. 12. ferroelectricity</li></li></ul><li>Objectives<br />By the end of this section you should:<br />be able to identify a unit cell in a symmetrical pattern<br />know that there are 7 possible unit cell shapes<br />be able to define cubic, tetragonal, orthorhombic and hexagonal unit cell shapes<br />3<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  13. 13. Why Solids?<br />most elements solid at room temperature<br /> atoms in ~fixed position<br />“simple” case - crystalline solid<br /> Crystal Structure<br />Why study crystal structures?<br />description of solid<br /> comparison with other similar materials - classification<br /> correlation with physical properties<br />4<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  14. 14. Crystals are everywhere!<br />5<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  15. 15. More crystals<br />6<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  16. 16. Early ideas<br />Crystals are solid - but solids are not necessarily crystalline<br />Crystals have symmetry (Kepler) and long range order<br />Spheres and small shapes can be packed to produces regular shapes (Hooke, Hauy)<br />7<br />?<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  17. 17. Group discussion<br />8<br />Kepler wondered why snowflakes have 6 corners, never 5 or 7. By considering the packing of polygons in 2 dimensions, demonstrate why pentagons and heptagons shouldn’t occur.<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  18. 18. Definitions1. The unit cell<br />“The smallest repeat unit of a crystal structure, in 3D, which shows the full symmetry of the structure”<br />9<br />The unit cell is a box with: <br /><ul><li> 3 sides - a, b, c
  19. 19. 3 angles - , , </li></ul>06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  20. 20.  Seven unit cell shapes<br /><ul><li>Cubic a=b=c ===90°
  21. 21. Tetragonal a=bc===90°
  22. 22. Orthorhombicabc===90°
  23. 23. Monoclinic abc==90°,   90°
  24. 24. Triclinic abc    90°
  25. 25. Hexagonala=bc==90°, =120°
  26. 26. Rhombohedrala=b=c ==90°</li></ul>Think about the shapes that these define - look at the models provided.<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />10<br />
  27. 27. 2D example - rocksalt(sodium chloride, NaCl)<br />11<br />We define lattice points ; these are points with identical environments<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  28. 28. Choice of origin is arbitrary - lattice points need not be atoms - but unit cell size should always be the same.<br />12<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  29. 29. This is also a unit cell - it doesn’t matter if you start from Na or Cl<br />13<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  30. 30. - or if you don’t start from an atom<br />14<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  31. 31. This is NOT a unit cell even though they are all the same - empty space is not allowed!<br />15<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  32. 32. In 2D, this IS a unit cellIn 3D, it is NOT<br />16<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  33. 33. All M.C. Escher works (c) Cordon Art-Baarn-the Netherlands.All rights reserved.<br />17<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  34. 34. Examples<br />18<br />The sheets at the end of handout 1 show examples of periodic patterns. On each, mark on a unit cell. [remembering that there are a number of different (correct) answers!]<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  35. 35. Summary<br />19<br /><ul><li>Unit cells must link up - cannot have gaps between adjacent cells
  36. 36. All unit cells must be identical
  37. 37. Unit cells must show the full symmetry of the structure  next section</li></ul>06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />
  38. 38. THANK YOU<br />06/01/2011<br />© 2010 Universitas Negeri Jakarta | www.unj.ac.id |<br />20<br />

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