Crystal Lattice Structures:	Creation Date: 25 Jan 1996
	Last Modified: 17 Feb 2007

The Body-Centered Tetragonal Lattice (A_a)

You can now

• see the structure from several perspectives;
• examine the structure with an external viewer; or
• download the coordinates of the atoms in these pictures in XYZ format.
• visualize the structure (Uses the JMOL Applet)

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• This is a body-centered tetragonal (bct) lattice, a distortion of the bcc lattice and the monatomic analog of the L1₀ structure. In addition, this structure has exactly the same symmetry as the A6 structure. In the A6 structure, c/a is near the fcc ratio of 2^1/2, while in the A_a structure, c/a is near the bcc ratio of 1.
• Also note that when
  c/a = (2/3)^½ = 0.816
  this system has a coordination of 10. In Pa the c/a ratio is 0.827.
• 17 Feb 2007: Gave the basis vector an atom type and Wyckoff position.

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• Prototype: αPa
• Pearson Symbol: tI2
• Strukturbericht Designation: A_a
• Space Group: I4/mmm (Cartesian and lattice coordinate listings available)
• Number: 139
• Other Elements with this Structure: In (See above) and βHg, where the c/a ratio is near
  2^-1/2.
• Reference: Pearson (Alloys), p. 562.
• Primitive Vectors:

  A1	=	a X
  A2	=	a Y
  A3	=	½ a X + ½ a Y + ½ c Z

• Basis Vector:

  B1 = 0 (Pa) (2a)

See these vectors in LaTeX output format.

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Structures indexed by: Strukturbericht Symbol Pearson Symbol Space Group Prototype

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