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2.3 Basic structure types

NiAs-type

Crystal data
Formula sum NiAs

Crystal system hexagonal

Space group P 63/m m c (no. 194)

Unit cell dimensions a = 3.619(1) Å, c = 5.025(1) Å
Z 2

Octahedra
Atomic coordinates

Atom Ox. Wyck. x y z Trigonal prisms

Ni1 +3 2a 0 0 0
As1 -3 2c 1/3 2/3 1/4

Structural features: Octahedron and
Structural features:
• all OH of HCP filled trig. prism
• Ni is coordinated by 6 As (octahedron)

• metal-metal-bonding (common faces of the octahedra)

• As is coordinated by 6 Ni (trigonal prism)

• type ≠antitype