The alpha Gallium Structure

The alpha Gallium Crystal Structure

Last modified 6 July 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.

The orientation used here is the one described in Pearson's Handbook and is consistent with the description of the Cmca space group in the International Tables for Crystallography. Note that Pearson's Handbook, Wyckoff's Crystal Structures, and the original Strukturbericht article each use a different orientation for the Gallium crystal.

Note, however, that Pearson's Handbook gives the information for an 8 atom orthorhombic cell. The unit cell described here is the 4 atom base-centered orthorhombic cell. The smaller cell is, of course, more efficient for electronic structure calculations.

Compare this structure to I₂ (A14) and P (black). The only difference is the degree of dimerization.

Prototype: alpha Ga
Pearson Symbol: oC8
Strukturbericht Designation: A11
Space Group: Cmca (Cartesian and lattice coordinate listings available)
Number: 64
Primitive Vectors:
- A₁ = ½ a X - ½ b Y
- A₂ = ½ a X + ½ b Y
- A₃ = c Z

Basis Vectors:

All atoms are on (8f) sites:

B₁	=	- u A₁ + u A₂ + v A₃	=	+ u b Y + v c Z
B₂	=	+ u A₁ - u A₂ - v A₃	=	- u b Y - v c Z
B₃	=	- (½ + u) A₁ + (½ + u) A₂ + (½ - v) A₃	=	(½ + u) b Y + (½ - v) c Z
B₄	=	- (½ - u) A₁ + (½ - u) A₂ + (½ + v) A₃	=	(½ - u) b Y + (½ + v) c Z

See these vectors in a better notation.

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