`BC8' Structure of Silicon

Last modified 5 July 2001

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.

This is a tetragonally bonded structure which packs more efficiently than diamond. It is seen experimentally in some silicon samples an is a staple for testing silicon potentials and first-principles calculations. This page of Stewart Clark's thesis has more information, as does the paper

J. Crain, S. J. Clark, G. J. Ackland, P. D. Hatton, B. J. Reid, M. C. Payne, and V. Milman, Phys. Rev. B 49, 5329 (1994).

Note that this structure is similar to the ST12 structure of silicon.

• Prototype: Si
• Pearson Symbol: cI16
• Space Group: Ia(-3) (Cartesian and lattice coordinate listings available)
• Number: 206
• Primitive Vectors:
  • A₁ = - ½ a X + ½ a Y + ½ a Z
  • A₂ = + ½ a X - ½ a Y + ½ a Z
  • A₃ = + ½ a X + ½ a Y - ½ a Z
• Basis Vectors [All atoms sit on the (16c) sites of the Ia(-3) space group. Note that the listed positions are based on an efficient expression of the atomic locations using the bcc primitive vectors, and are related to the positions listed in the International Crystallographic Tables by a translation.]
  • B₁ = + 2 x A₁ + 2 x A₂ + 2 x A₃ = + x a X + x a Y + x a Z
  • B₂ = - 2 x A₁ - 2 x A₂ - 2 x A₃ = - x a X - x a Y - x a Z
  • B₃ = + (½ - 2 x) A₁ + ½ A₂ = + x a X - x a Y + (½ - x) a Z
  • B₄ = - (½ - 2 x) A₁ - ½ A₂ = - x a X + x a Y - (½ - x) a Z
  • B₅ = + (½ - 2 x) A₂ + ½ A₃ = + (½ - x) a X + x a Y - x a Z
  • B₆ = - (½ - 2 x) A₂ - ½ A₃ = - (½ - x) a X - x a Y + x a Z
  • B₇ = + ½ A₁ + (½ - 2 x) A₃ = - x a X + (½ - x) a Y + x a Z
  • B₈ = - ½ A₁ - (½ - 2 x) A₃ = + x a X - (½ - x) a Y - x a Z

See these vectors in a better notation.

Go back to The Carbon Structures page.

Go back to The Crystal Lattice Structure page.

Structures indexed by:

• Strukturbericht Designation
• Pearson Symbol
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