The Ideal beta Cristobalite Structure

Last modified 13 April 2001

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This is the idealized version of the high-temperature phase of alpha Cristobalite. Pearson's Handbook says that the the Si atoms partially occupy the (96g) positions in the Fd(-3)m space group.

The silicon atoms occupy the positions they take in the diamond (A4) structure, while the oxygen atoms form bridges between them.

• Prototype: SiO₂ (ideal beta-Cristobalite)
• Pearson Symbol: cF24
• Strukturbericht Designation: C9
• Space Group: Fd(-3)m (Cartesian and lattice coordinate listings available)
• Number: 227
• Primitive Vectors:
  • A₁ = ½ a Y + ½ a Z
  • A₂ = ½ a X + ½ a Z
  • A₃ = ½ a X + ½ a Y
• Basis Vectors:

  B1	=	+ 1/8 A1 + 1/8 A2 + 1/8 A3	=	+ 1/8 a X + 1/8 a Y + 1/8 a Z	(8a)	(Si)
  B2	=	- 1/8 A1 - 1/8 A2 - 1/8 A3	=	- 1/8 a X - 1/8 a Y - 1/8 a Z	(8a)	(Si)
  B3	=		0		(16c)	(O)
  B4	=	¼ A2 + ¼ A3	=	1/4 a X + 1/8 a Y + 1/8 a Z	(16c)	(O)
  B5	=	¼ A1 + ¼ A3	=	1/8 a X + 1/4 a Y + 1/8 a Z	(16c)	(O)
  B6	=	¼ A1 + ¼ A2	=	1/8 a X + 1/8 a Y + 1/4 a Z	(16c)	(O)

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