The alpha La (A3') Structure

Last modified 7 July 2001

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• see the structure from several perspectives;
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This lattice is a closepacked, with stacking ABACABAC..., as opposed to ABAB... for the hcp (A3) lattice and ABCABC... for the fcc (A1) lattice. The (2a) crystallographic sites (the A's) form a simple hexagonal lattice. The (2c) sites (the B's and C's) form an hcp lattice.

• Prototype: alpha La
• Pearson Symbol: hP4
• Strukturbericht Designation: A3'
• Space Group: P6₃/mmc (Cartesian and lattice coordinate listings available)
• Number: 194
• Other Elements with this Structure:
• Primitive Vectors:
  • A₁ = ½ a X - ½ 3^1/2 a Y
  • A₂ = ½ a X + ½ 3^1/2 a Y
  • A₃ = c Z

• Basis Vectors:
  • B₁ = 0 (2a)
  • B₂ = 1/2 A₃ = ½ c Z (2a)
  • B₃ = 1/3 A₁ + 2/3 A₂ + ¼ A₃ = ½ a X + ½ 3^-1/2 a Y + ¼ c Z (2c)
  • B₄ = 2/3 A₁ + 1/3 A₂ + ¾ A₃ = ½ a X - ½ 3^-1/2 a Y + ¾ c Z (2c)

See these vectors in a better notation.

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