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

The (Original) Moissanite-4H CSi Crystal Structure

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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 (B3,4) 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.

• 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: 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).