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

The (Original) 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 the original version of this page. Now that we have actual experimental data, we have constructed a new Moissanite-4H page.
• This is a hypothetical alternate 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.
• 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 = 2 (8/3)^1/2.
• The positions of the C-II atoms (B_3,4) aren't in the usual order for space group P6₃mc. To get them in the order used in the Crystallography Tables take z₂ -> z₂ + ½.

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• Prototype: CSi
• Pearson Symbol: hP8
• Space Group: P6₃mc (Cartesian and lattice coordinate listings available)
• Number: 186
• Primitive Vectors:

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

• Basis Vectors:

  The ``ideal'' positions of the atoms in the this structure are:

  z1 = 0 (Of course, we can always choose one of the zi = 0)

  z2 = 1/4

  z3 = 3/16

  z4 = 7/16

  B1	=	z1A3	=	z1c Z	(C-I)	(2a)
  B2	=	½ + z1 A3	=	(½ + z1) c Z	(C-I)	(2a)
  B3	=	2/3 A1 + 1/3 A2 + z2 A3	=	½ a X - 12-½ a Y + z2 cZ	(C-II)	(2b)
  B4	=	1/3 A1 + 2/3 A2 + (½ + z2) A3	=	½ a X + 12-½ a Y + (½ + z 2) c Z	(C-II)	(2b)
  B5	=	z3 A3	=	z3 c Z	(Si-I)	(2a)
  B6	=	½ + z3 A3	=	(½ + z3) c Z	(Si-I)	(2a)
  B7	=	1/3 A1 + 2/3 A 2 + z4 A3	=	½ a X + 12-½ a Y + z4 c Z	(Si-II)	(2b)
  B8	=	2/3 A1 + 1/3 A2 + (½ + z4) A3	=	½ a X - 12-½ a Y + (½ + z4) c Z	(Si-II)	(2b)

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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).