The AlCCr₂ Structure

Last modified 18 September 2001

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.

Note that all of the atoms sit on close packed <0001> planes. The stacking sequence may be written

Thus the C and Cr atoms are always in an fcc-like local environment, while the Al atoms are in an hcp-like local environment.

• Prototype: AlCCr₂
• Pearson Symbol: hP8
• Space Group: P6₃/mmc (Cartesian and lattice coordinate listings available)
• Number: 194
• Other compounds with this structure: Cr₂GaN, CeGeLi₂, many others
  MAX phases: AlCNb₂, AlCTi₂, AlNTi₂, AsCNb₂, CCrGe₂, AlCV₂, more.
• Primitive Vectors:

  A1  =	½ a X - ½ 31/2 a Y
  A2  =	½ a X + ½ 31/2 a Y
  A3  =	c Z

• Basis Vectors:

  B1  =			0			(C)	(2a)
  B2  =	½ A3		=	½ c Z		(C)	(2a)
  B3  =	2/3 a A1  + 1/3 a A1  +	¼ A3	=	½ a X - ½ 3-1/2 a Y +	¼ c Z	(Al)	(2d)
  B4  =	1/3 a A1  + 2/3 a A1  +	¾ A3	=	½ a X + ½ 3-1/2 a Y +	¾ c Z	(Al)	(2d)
  B5  =	2/3 a A1  + 1/3 a A1  -	z A3	=	½ a X + ½ 3-1/2 a Y -	z   c Z	(Cr)	(4f)
  B6  =	1/3 a A1  + 2/3 a A1  +	z A3	=	½ a X - ½ 3-1/2 a Y +	z   c Z	(Cr)	(4f)
  B7  =	1/3 a A1  + 2/3 a A1  +	(½ - z) A3	=	½ a X + ½ 3-1/2 a Y +	(½ - z) c Z	(Cr)	(4f)
  B8  =	2/3 a A1  + 1/3 a A1  +	(½ + z) A3	=	½ a X - ½ 3-1/2 a Y +	(½ + z) c Z	(Cr)	(4f)

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