Crystal Lattice Structures:	Creation Date:  1 Jul 2001
	Last Modified: 21 Oct 2004

The Moissanite-9R CSi Crystal Structure

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 hypothetical alternate stacking (ABCBCACAB) for tetrahedral structures. Compare this to Zincblende (ABCABC), Wurtzite (ABABAB), and 6H (ABCACB). The 9R refers to the fact that there are 9 CSi dimers in a hexagonal unit cell (which contains 3 rhombohedral unit cells). Zincblende is denoted 3C, and Wurtzite is 2H.
• This structure is related to the αSm (C19) structure in the same way that Zincblende (B3) is related to the fcc (A1) lattice.
• The spacings in structure file assume that the local environment is similar to Zincblende CSi. Thus the internal parameters have the values given in the table below, and c/a = (9/2) (8/3)^½.

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• Prototype: CSi
• Pearson Symbol: hR6
• Space Group: R3m (Cartesian and lattice coordinate listings available)
• Number: 160
• Primitive Vectors:
  • a and c are the lattice constants of the equivalent hexagonal unit cell.

  A1	=	+ ½ a X + ½ 3-1/2 a Y + 1/3 c Z
  A2	=	- ½ a X + ½ 3-1/2 a Y + 1/3 c Z
  A3	=	- 3-1/2 a Y + 1/3 c Z

• Basis Vectors:
  • All atoms are on (1a) Wyckoff positions. The 'ideal' structure parameters, those that get us closest to the Zincblende structure, are:

    x1 = 0

    x2 = - 2/9

    x3 = + 2/9

    x4 = 3/36

    x5 = 11/36

    x6 = -5/36

  B1	=	x1 (A1 + A2 + A3)	=	x1 c Z	(C-I)	(1a)
  B2	=	x2 (A1 + A2 + A3)	=	x2 c Z	(C-II)	(1a)
  B3	=	x3 (A1 + A2 + A3)	=	x3 c Z	(C-III)	(1a)
  B4	=	x4 (A1 + A2 + A3)	=	x4 c Z	(Si-I)	(1a)
  B5	=	x5 (A1 + A2 + A3)	=	x5 c Z	(Si-II)	(1a)
  B6	=	x6 (A1 + A2 + A3)	=	x6 c Z	(Si-III)	(1a)

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Structures indexed by: Strukturbericht Symbol Pearson Symbol Space Group Prototype

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