Crystal Lattice Structures:	Creation Date: 22 Mar 2003
	Last Modified: 21 Oct 2004

The Moissanite-4H 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 new version of the Moissanite-4H page which reflects the experimental data. The original Moissanite-4H page remains available.
• This is one possible stacking (ABAC) for tetrahedral structures. Compare this to Zincblende (ABCABC), Wurtzite (ABABAB), 6H (ABCACB), and 9R (ABCBCACAB). The 4H refers to the fact that there are 4 CSi dimers in a hexagonal unit cell. Zincblende is denoted 3C, and Wurtzite is 2H.
• This structure is related to the αLa (A3') structure in the same way that Zincblende (B3) is related to the fcc (A1) lattice.
• Bauer et al. put the atoms on non-standard crystallographic positions. We reordered the structure to place the atoms on standard sites.
• The Carbon-Silicon atom distance could not be determined from the experimental data. We take set the C-Si distances

  (z₂ - z₁) c = (z₄ - z₃) c = 3/16 c

  i.e., the same as they would be in the ideal structure.
• Without loss of generality, we can take any of the z_i to be zero. In the pictures here we take z₁ = 0.

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• Prototype: CSi
• Pearson Symbol: hP8
• Space Group: P6₃mc (Cartesian and lattice coordinate listings available)
• Number: 186
• Reference: A. Bauer et al., Acta Cryst. A 57, 60 (2001).
• Primitive Vectors:

  A1	=	½ a X - ½ 3½ a Y
  A2	=	½ a X + ½ 3½ a Y
  A3	=	c Z

• Basis Vectors:

  B1	=	z1 A3	=	z1 c Z	(Si-I)	(2a)
  B2	=	(½ + z1) A3	=	(½ + z1) c Z	(Si-I)	(2a)
  B3	=	z2 A3	=	z2 c Z	(C-I)	(2a)
  B4	=	(½ + z2) A3	=	(½ + z2) c Z	(C-I)	(2a)
  B5	=	1/3 A1 + 2/3 A2 + z3 A3	=	½ a X + 12-½ a Y + z3 c Z	(Si-II)	(2b)
  B6	=	2/3 A1 + 1/3 A2 + (½ + z3) A3	=	½ a X - 12-½ a Y + (½ + z3) c Z	(Si-II)	(2b)
  B7	=	1/3 A1 + 2/3 A2 + z4 A3	=	½ a X + 12-½ a Y + z4 c Z	(C-II)	(2b)
  B8	=	2/3 A1 + 1/3 A2 + (½ + z4) A3	=	½ a X - 12-½ a Y + (½ + z4) c Z	(C-II)	(2b)

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