Term
| Cubic Axial lengths and angles |
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Definition
| a=b=c, alpha=beta=gamma=90 degrees |
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Term
| Tetragonal Axial lengths and angles |
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Definition
| a=b not=c, alpha=beta=gamma=90 degrees |
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Term
| Orthorhombic Axial lengths and angles |
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Definition
| a NE b NE c, alpha=beta=gamma=90 degrees |
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Term
| Rhombohedral Axial lengths and angles |
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Definition
| a=b=c, alpha=beta=gamma NE 90 degrees |
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Term
| Hexagonal Axial lengths and angles |
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Definition
| a=b NE c, alpha=beta=90 degrees, gamma=120 degrees |
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Term
| Monoclinic Axial lengths and angles |
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Definition
| a NE b NE c, alpha=gamma=90 degrees NE beta |
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Term
| Triclinic Axial lengths and angles |
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Definition
| a NE b NE c, alpha NE beta NE gamma NE 90 degrees |
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Term
| Three crystal structures of most elemental metals at room temperature |
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Definition
Body-centered cubic (bcc)
Face-centered cubic (fcc)
Hexagonal close packed (hcp) |
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Term
Atomic packing factor (APF)
equation |
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Definition
Fraction of the unit cell volume occupied by the atoms
APF=N(atoms)V(atoms)/V(crystal) |
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Term
| Body-centered cubic (bcc) |
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Definition
One atom at the center of the unit cell
One-eighth atom at each corner
Two atoms in each bcc unit cell
Bcc metals: -Fe, V, Cr, Mo, W
Unit cell face lenght a=4r/sqrt(3) |
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Term
| Face-centered cubic (fcc) |
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Definition
One-half atom in the center of each face
One-eight atom at each corner
Four atoms in each fcc unit cell
Fcc metals: -Fe, Al, Ni, Cu, Ag, Pt, Au
a=4r/sqrt(2) |
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Term
| Hexagonal close packed (hcp) |
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Definition
Based on hexagonal Bavais lattice
Two atoms associated with Bravais lattice point
One atom centered within the unit cell, various fraction atoms at corners (four 1/6, four 1/12 atoms)
Total of 2 atoms in unit cell
APF=0.74
Hcp material: Be, Mg, -Ti, Zn, Zr |
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