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Ionic solids with formula Mx

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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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