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Ionic solids with formula Mx

Ionic solids with formula Mx. 201101021 박한솔. Contents. Basic crystal structure Metallic Crystals Structures of ionic solids with formula MX. Basic crystal structure. The primitive cubic structure - The most basic crystal structure, called simple cubic - All layers is identical

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Ionic solids with formula Mx

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  1. Ionic solids with formula Mx 201101021 박한솔

  2. Contents • Basic crystal structure • Metallic Crystals • Structures of ionic solids with formula MX

  3. Basic crystal structure • The primitive cubic structure • - The most basic crystal structure, called simple cubic • - All layers is identical • - Total number of atoms in the unit cell (z) = 8 x 1/8 = 1 • - Coordination number (CN) is 6 • - Occupancy = 52.4% , 0.73r sphere

  4. Basic crystal structure • 2. Body-Centered Cubic • Another sphere is added in the center of the simple cubic structure • CN = 8 • Occupancy is 68% • If the added sphere has the same radius as others it has 2.31r

  5. Basic crystal structure • 3. Close-Packed Structures • Hexagonal Close Packing (hcp) • The result of an ABA structure • CN = 12 ( 6 in the same layer, 3 in layer above and 3 in layer below) • Occupancy is 74%

  6. Basic crystal structure • 3. Close-Packed Structures • (2) Cubic Close Packing(ccp) or Face-Centered Cubic(fcc) • The result of ABC structure • CN = 12 • Occupancy is 74% • Unit cell is Face-centered cubic

  7. Basic crystal structure • 4. Holes in Lattices • The packing of atoms into carious lattices produces interstices or “holes”, which may be filled to produce different compounds • Two different types of holes in close-packed structures

  8. Basic crystal structure • (1) Tetrahedral holes • CN = 4 • Radius of the largest sphere fit in the tetrahedral holes = 0.225r • (2) Octahedral holes • CN = 6 • Radius of the largest sphere fil in the octahedral holes = 0.414r

  9. Metallic crystals • Most metals crystalize in body-centered cubic(bcc), cubic close-packed(ccp), and hexagonal close-packed structures(hcp) • Changes in pressure or temperature can change metallic crystals • The sizes and packing of atoms are somewhat variable

  10. Metallic crystals • Properties of Metals • High conductivity ( low resistance) to the passage of electricity and of heat • Some are soft and easily deformed by pressure or impact, or malleable (Cu, fcc) • Some are hard and brittle (Zn, hcp) (rare) • Boding is non-directional • Dislocation

  11. Structures of ionic solids with formula MX • ※ the relative sizes of the atoms or ions • The radius ration(r+/r-) • Small cations can fit in the tetrahedral or octahedral holes of a close-packed anion lattices • Lager cations can if in the octahedral holes, but not in tetrahedral holes

  12. Structures of ionic solids with formula MX • ※ the relative numbers of cations and anions • Formula M2X will not allow a close-packed anion lattice and occupancy of all the octahedral holes by the cations

  13. Structures of ionic solids with formula MX • Caesium chloride structure (CsCl) • Simple primitive cubic of Cl • Cs in the centers • CN = 8 (both) • - CsCl, CaS, TlCl, CsCN

  14. Structures of ionic solids with formula MX • (2) Sodium chloride (NaCl) • Known as rock salt • Unit cell is cubic • Consist of two interpenetrating • face-centered arrays • CN = 6 • Usually with the anions larger than • the cations • Many alkali halides • LiCl, KBr, MgO, AgCl, TiO, NiO, ScN

  15. Structures of ionic solids with formula MX • (2) Sodium chloride (NaCl)

  16. Structures of ionic solids with formula MX • (2) Sodium chloride (NaCl) • Alternative way of viewing • this structure • The close packing of one of • the ions

  17. Structures of ionic solids with formula MX • (2) Sodium chloride (NaCl)

  18. Structures of ionic solids with formula MX • (2) Sodium chloride (NaCl) • The other way to see “NaCl”

  19. Structures of ionic solids with formula MX • MO6 octahedral link through • A vertex : M2O11 • An edge : M2O10 • A face : M2O9

  20. Structures of ionic solids with formula MX • NaCl structure -> NaCl6 octahedral sharing edges

  21. Structures of ionic solids with formula MX • (3) Nickel arsenide (NiAs) structure • Arsenic atoms in identical close-packed layers • Nickel atoms in all the octahedral holes • of a hexagonal close-packed arsenic lattice • CN = 6 (both) • MX compounds • M = transition metal • X = Group 14, 15 or 16 • (Sn, As, Sb, Bi, S, Se, or Te)

  22. Structures of ionic solids with formula MX • (4) Zinc blende or Sphalerite (ZnS) • CN = 4 • The most common zinc ore • The same geometry as diamond • if all the atoms were identical • Each in face-centered lattices • Each ions in a tetrahedral hole of the other latice • The copper halides (CuX), Zn, Cd, Hg with sulfides

  23. Structures of ionic solids with formula MX • (5) Wurtzite (ZnS) • - Polymorph(동질이상) with zinc blende • CN = 4 • Much rare than zinc blends • Formed at higher temperature • Each in a tetrahedral hole of the other • lattice • Each ion forms a hexagonal close-pack • Lattice • - BeO, ZnO, and NH4F

  24. Structures of ionic solids with formula MX

  25. Thank you

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