Crystal Lattice Structures: Creation Date: 27 Mar 1998 Last Modified: 21 Oct 2004

# `BC8' Structure of Silicon

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• 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.
• All atoms sit on the (16c) sites of the Ia3 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.

• Prototype: Si
• Pearson Symbol: cI16
• Space Group: Ia3 (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:  B1 = + 2 x A1 + 2 x A2 + 2 x A3 = + x a X + x a Y + x a Z (Si) (16c) B2 = - 2 x A1 - 2 x A2 - 2 x A3 = - x a X - x a Y - x a Z (Si) (16c) B3 = + (½ - 2 x) A1 + ½ A2 = + x a X - x a Y + (½ - x) a Z (Si) (16c) B4 = - (½ - 2 x) A1 - ½ A2 = - x a X + x a Y - (½ - x) a Z (Si) (16c) B5 = + (½ - 2 x) A2 + ½ A3 = + (½ - x) a X + x a Y - x a Z (Si) (16c) B6 = - (½ - 2 x) A2 - ½ A3 = - (½ - x) a X - x a Y + x a Z (Si) (16c) B7 = + ½ A1 + (½ - 2 x) A3 = - x a X + (½ - x) a Y + x a Z (Si) (16c) B8 = - ½ A1 - (½ - 2 x) A3 = + x a X - (½ - x) a Y - x a Z (Si) (16c)

### See these vectors in LaTeX output format.

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 Structures indexed by: This is a mirror of an old page created at theNaval Research LaboratoryCenter for Computational Materials ScienceThe maintained successor is hosted at http://www.aflowlib.org/CrystalDatabase/ and published as M. Mehl et al., Comput. Mater. Sci. 136 (Supp.), S1-S828 (2017).