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

`BC8' Structure of Silicon

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 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.

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• 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: Strukturbericht Symbol Pearson Symbol Space Group Prototype

This is a mirror of an old page created at the Naval Research Laboratory Center for Computational Materials Science The 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).