physics unit 1
DESCRIPTION
this ppt is clearly about the crystal physics.....conceptTRANSCRIPT
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Crystal Physics
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Lattice• Regular , periodical arrangements of points in
three dimension.• Lattice point : The points which presents in the
lattice
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Basis
• Group of atom is called as basis
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Crystal structure
• Lattice + basis = crystal structure• Crystal structure is obtained by arranging the
basis in each and every lattice point
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Unit cell
• Smallest geometric figure , by the repetition of this we get complete crystal structure.
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Crystal parameters • The three mutual perpendicular lines OX,OY
and OZ.• Inter axial lengths: OA = a , OB = b and OC = c• Inter axial angles: α,β and γ
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Crystal system
CubicOrthorhombicMonoclinicTriclinicHexagonalRhombohedralTetragonal
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Bravais lattice
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Lattice planes
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Miller indices
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d spacing in cubic lattice
222 lkh
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Calculation of number of atoms per unit cell – Atomic radius –
Coordination number – Packing factor for SC , BCC ,FCC and HCP
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Simple Cubic structure
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Atomic radius(r)
• r = a/2
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Coordination number (N)
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Body Centered Cubic
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Number of atoms per unit cell
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Coordination number
• For BCC the coordination number is 8
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Face Centered Cubic
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• Atomic radius = a √2 / 4
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HCP
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Na Cl structure
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ZnS Structure
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diamond and graphite Structure
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Polymorphism and allotropy • Polymorphism is a physical phenomenon where
a material may have more than one crystal structure.
• A material that shows polymorphism exists in more than one type of space lattice in the solid state. If the change in structure is reversible, then the polymorphic change is known as allotropy.
• The prevailing crystal structure depends on both the temperature and the external pressure.
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• Allotropes of carbonDiamond and graphite
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Crystal defects
• Point defect• line defect • surface defect• Burger vector
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Point defect
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Line defect
![Page 32: Physics unit 1](https://reader033.vdocument.in/reader033/viewer/2022061214/549a16f5b4795937378b45b5/html5/thumbnails/32.jpg)
Burger vector
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Dislocations
![Page 34: Physics unit 1](https://reader033.vdocument.in/reader033/viewer/2022061214/549a16f5b4795937378b45b5/html5/thumbnails/34.jpg)
Surface defects
• Grain boundary• Tilt boundary• Twin boundaries• Stacking fault
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Thank you for your patience