Introduction and point groups

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Introduction and point groups Stereographic
projections Low symmetry systems Space
groups Deformation and texture Interfaces,
orientation relationships Martensitic
transformations
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Introduction
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Form
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Anisotropy
Ag
Mo
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Polycrystals
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The Lattice
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Centre of symmetry and inversion
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Bravais Lattices

• Triclinic P
• Monoclinic P C
• Orthorhombic P, C, I F
• Tetragonal P I
• Hexagonal
• Trigonal P
• Cubic P, F I

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Bravais Lattices
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2D lattices
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Crystal Structure
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lattice motif structure
primitive cubic lattice motif Cu at 0,0,0
Zn at 1/2, 1/2, 1/2
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Lattice face-centred cubic Motif C at 0,0,0
C at 1/4,1/4,1/4
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1/4
3/4
1/4
3/4
Lattice face-centred cubic Motif Zn at 0,0,0
S at 1/4,1/4,1/4
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fluorite
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Point groups
2m
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Water and sulphur tetrafluoride have same point
symmetry and hence same number of vibration modes
- similar spectra
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Gypsum 2/m
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Epsomite 222
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2/m
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mm2
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4/m mm or 4/mmm
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Weiss Law

• If a direction uvw lies in a plane (hkl) then
• uhvkwl 0

uvw
(hkl)
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