web3 - CHEM 313 From molecules to the SOLID: is the solid...

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CHEM 313 1 Extended structures no localized chemical reactivity low mobility of constituents From molecules to the SOLID: is the solid state special? large activation energies for reactions high reaction temperatures/thermodynamic control phase diagrams important for chemical reactions experiments under extreme physical conditions: 1 very high pressures and temperatures description in terms of structure types packing/coordination polyhedra vs. molecular units From molecules to the SOLID: is the solid state special? Frequently used classifications for solids a) elements : new modifications (e.g. fullerenes), structure comparisons, growth of high purity crystals . .. b) crystalline materials : synthesis and crystal growth, defects, structure – chemical bonding – physical properties . .. c) noncrystalline/amorphous materials : special physical and chemical properties . .. d) (quasi)molecular solids (e.g. phosphides) : structural relations . .. e) covalent solids (e.g. diamond, boron nitride) : extreme hardness, very 2 high melting points . .. f) ionic solids (e.g. NaCl) : structural chemistry, ionic conductivity . .. g) metals, semiconductors, isolators : close packings of spheres, alloys, mechanical and electrical properties, chemical bonding . ..
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CHEM 313 2 Crystalline Solids and Crystallography Mechanical Properties Electrical Properties Metals/Alloys, e.g. Titanium for aircraft Cement/Concrete Ca 3 SiO 5 'Ceramics', e.g. clays, BN, SiC Lubricants, e.g. Graphite, MoS 2 Abrasives, e.g. Diamond, Corundum Magnetic Properties Optical Properties Metallic Conductors, e.g. Cu, Ag . .. Semiconductors, e.g. Si, GaAs Superconductors, e.g. Nb 3 Sn, YBa 2 Cu 3 O 7 Electrolytes, e.g. LiI in pacemakers Piezoelectrics, e.g. -Quartz in watches CrO 2 , Fe 3 O 4 for recording technology Pigments, e.g. TiO 2 in paints 3 Catalysts Phosphors, e.g. Eu 3+ in Y 2 O 3 is red on TV Lasers, e.g. Cr 3+ in Al 2 O 3 is ruby Zeolite ZSM-5 (an aluminosilicate) - Petroleum refining - methanol to octane Solid State Chemistry - Permutations Example Superconducting Tc (K) Elements - A 80-106 (known) Nb (9) Binary - AB (80 x 79)/2 = 3160 (known) Nb 3 Ge (23) Mg 3 B 2 (39) Ternary - ABC (80 x 79 x 78)/6 (5% known) La 2 CuO 4 (40) Quaternary - ABCD 1.5 M (surface scratched) YBa 2 Cu 3 O 7 (93) ABCDE Gazillions (trace) HgBa 2 Cu 3 O 4 (135) 4
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CHEM 313 3 CRYSTAL STRUCTURE UNIT CELL The periodic arrangement of atoms in the crystal. The smallest component of the crystal, which when replicated in (one, two or) three dimensions reproduces the whole crystal. The solid state: some basic definitions 5 The solid state: some basic definitions The unit cell “The smallest repeat unit of a crystal structure, in 3D, which shows the full symmetry of the structure” 6 Atomic position: ( x , y , z ) (fractional coordinates)
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CHEM 313 4 The solid state: some basic definitions Atoms in different positions in a unit cell are shared by differing numbers of unit cells Counting Atoms in 2D unit cells Atoms at the corner of the 2D unit cell contribute only 1/4 to unit cell count Atoms at the edge of the 2D unit cell contribute only 1/2 to unit cell count Atoms within
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This note was uploaded on 02/28/2011 for the course CHEM 313 taught by Professor Prof.holgerkleinke. during the Spring '11 term at Waterloo.

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web3 - CHEM 313 From molecules to the SOLID: is the solid...

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