Crystal Lattice Structures:	Creation Date:  7 Jul 2008
	Last Modified:  7 Jul 2008

The Monoclinic (Cc) Low Tridymite (SiO₂) 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 one of the low temperature, low symmetry forms of Tridymite.

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• Prototype: Monoclinic (Cc) Low Tridymite (SiO₂)
• Pearson Symbol: mC144
• Strukturbericht Designation: None
• Space Group: Cc (Cartesian and lattice coordinate listings available)
• Number: 9
• Reference: W. A. Dollase and W. H. Baur, Am. Min. 61 971-8 (1976).
• Primitive Vectors (Unique Monoclinic Axis b):

  A1	=	½ a X - ½ b Y
  A2	=	½ a X + ½ b Y
  A3	=	c cosβ X + c sinβ Z

• Basis Vectors:
  
  Space Group Cc (#9) has only one Wyckoff position with two operations, while Cc-Trydymite has 72 atoms in the primitive unit cell. Rather than printing out the same pair of equations 36 times, we present one pair of equations, and note that the position label α represents a Silicon atom for α ≤ 12 and an Oxygen atom otherwise.

  B2α-1	=	+ (xα - yα) A1 + (xα + yα) A2 + zα A3	=	+ [ xα a + zα c cosβ ] X + yα b Y + zα c sinβ Z		(4a)
  B2α	=	+ (xα + yα) A1 + (xα - yα) A2 + (½ + zα) A3	=	+ [ xα a + (½ + zα) c cosβ ] X - yα b Y + (½ + zα) c sinβ Z		(4a)

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