lec3.pdf
DESCRIPTION
PHYSICSTRANSCRIPT
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BITS Pilani Hyderabad Campus
CRYSTAL STRUCTURE
Meenakshi Viswanathan
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BITS Pilani, Hyderabad Campus
Classification of Crystal Lattice
SYMMETRY
Inversion – All Bravais lattices are inversion
symmetric
Reflection
Rotation – only 2, 3, 4 & 6 fold rotations are
possible
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BITS Pilani, Hyderabad Campus
Possible 2-D Lattice types
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BITS Pilani, Hyderabad Campus
SYMMETRY IN CRYSTALS
One of the beautiful qualities of solids is that they are often crystals of extraordinary regularity and shape. There are also other regular patterns one sees often, e.g., tile on a floor. Below are three figures of typical tile patterns. Imagine that each pattern extends to infinity in all directions. Describe any symmetry that you see in each of the patterns. For example, the pattern on the top left is the same if it is rotated by 180 degrees. Thus it is symmetric under 180 degree rotations. Are there other rotations that leave the pattern the same? Are there reflections that leave the pattern the same, i.e., if a mirror were placed vertically on the floor in a certain orientation, would the pattern look the same in the mirror?
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
Tetragonal Bravais Lattice
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BITS Pilani, Hyderabad Campus
Orthorhombic Bravais Lattice
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BITS Pilani, Hyderabad Campus
Simple Hexagonal Bravais Lattice
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BITS Pilani, Hyderabad Campus
HCP Structure
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
Diamond Lattice
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BITS Pilani, Hyderabad Campus
NaCl
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus
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BITS Pilani, Hyderabad Campus