Chapter 6 Solid-State Chemistry
Problems n n 6.9, 6.13, 6.14
Unit Cells?
Unit Cells 7 types n n cubic n n orthorhombic n n tetragonal n n hexagonal n n monoclinic n n triclinic n n trigonal/rhombohedral
Bravais Lattices n n 14 n n Figure 6.1, pg. 253
Space Groups n n 235 discrete structural arrangements n n some selected crystal systems n Table 6.1, pg. 254
Top 6 Space Groups n n as reported in literature n P2 1 /c29.2%monoclinic n P orthorhombic n P triclinic n P monoclinic n C2/c 5.4monoclinic n Pnma 1.5orthorhombic n P orthorhombic
Structure Determination
Diffraction Conditions
n Solid-State Resources CD n Chapter 4 Diffraction n Quicktime Movie
Diffraction Conditions
Why monochromatic radiation?
Why use the shorter wavelength?
Reciprocal Lattice
Optical Transforms n Solid-State Resources CD n Chapter 4 Diffraction n Quicktime Movies
Discovery Slide
VSEPR Slide
Powder Diffraction Line spectrum for BaTi Zr O
Powder Diffraction n n ASTM cards n n dissertation
Single Crystal n n diffractometer n goniometer
X-ray Diffractometer
X-ray Diffractometer with CCD Detector
Goniometer Head for Single Crystal
Miller Indices n describe which plane of atom is interacting with the x-rays n used to calculate the reciprocal lattice parameters
Miller Indices
Reciprocal Lattice Cubic (1/d hkl ) = (h 2 + k 2 + l 2 ) 1/2 /a
Reflection Intensity |F o | " p I n n positive or negative root n n “phase problem” n n solve using Patterson methods when heavy atom is present n n solve using direct methods
Estimate of Error R = | F o - F c | / F o
Systematic Absences n n laser & ICE slides
Grains and Close Packing in Metals Grains in a polycrystalline material
Defects in Solids n Solid-State Resources CD n Chapter 6 Diffraction n Quicktime Movies
Dislocations
Work Hardening
Band Theory
Bands
Bands in Metals
Optical Properties of Metals Some possible electronic transitions in a half-filled band of a metal
Metallic Sea of Electrons High thermal conductivity High electrical conductivity High reflectivity of visible light Electrons are not bonded to any particular atom and are free to move about in the solid.
Electrical Conductivity Conductivity ( -cm ) –1
Electrical Conductivity Conductivity of metals decreases with temperature as atomic vibrations scatter free electrons. Conductivity of semiconductors increases with temperature as the number of carriers increases.
Bands and Electrical Conductivity n Solid-State Resources CD n Chapter 7 Bonding n Quicktime Movies n start with Movie Sand Bands n end with Movie Photocell
Optical Properties of Semiconductors
Band Gap Energy and Color
Semiconductors
Semiconductors two requirements n average number of valence shell electrons equals four n diamond (pure Si or Ge) crystal structure n or zinc blende (1:1 stoichiometry) crystal structure
Band Gap and Periodic Properties ElementUnit Cell, ÅD o, kJ/molE g, eV (, nm) C (230) Si (1100) Ge (1900) -Sn < 0.1(12,000) MaterialUnit Cell, Ų E g, eV (, nm) Ge (1900) GaAs (890) ZnSe (460) CuBr (430)
Solid Solutions 0.0 AZ AZ AZ 0.6 AZ AZ AZ 0.0
Semiconductors n Solid-State Resources CD n Chapter 7 Bonding n Quicktime Movies n start with Picture Periodic n end with Movie LED under Microscope
Buckminsterfullerenes C 60 & C 70 n n allotrope of carbon n n fcc n n lubricants, organic magnets, frequency doubling materials, and substrates for growing diamonds
Buckminsterfullerenes M 3 C 60 n n high temperature superconductor
Buckminsterfullerenes
Superconductivity n n Hg was discovered to be superconducting ar 4 K in 1911 n n many other metals are superconducting < 10 K (Al family, Sn, Pb, Ti, V, Zn, Cd, several 2nd & 3rd transition series) n n some alloys
Superconductivity n n Superconductors (MBa 2 Cu 3 O 7-8 ) n n liquid nitrogen temperature superconductors
Superconductivity n n Loss of Resistance n Cooper pairs n n Meissner Effect
Superconductivity n n Perovskite n CaTiO 3
Superconductivity n Solid-State Resources CD n Chapter 9 Thermodynamics n Quicktime Movies n start with Movie Superconductivity Setup n end with Movie Superconductivity Small Magnet