Nickel arsenide NiAs

Unit cell

Lattice constants

a = 3.602 Å, b = 3.602 Å, c = 5.009 Å; α = 90°, β = 90°, γ = 120°

Cell volume

56.3 ų

Atoms in the cell

4 (Ni 2, As 2)

Formula units Z

2

Calculated density

7.88 g cm⁻³

Shortest contact

2.428 Å

Coordination

Ni

CN 6 at 2.43 Å (6 As)

As

CN 6 at 2.43 Å (6 Ni)

About the structure

• hcp array of As with Ni in every octahedral hole — the hcp counterpart of rock salt.
• Ni is octahedral; As sits in a trigonal prism of six Ni.
• The Ni–Ni distance along c (2.50 Å) is short enough for metal–metal bonding; many NiAs-type compounds are metallic.
• FeS, CoS, NiS, FeSe adopt this structure.

Atom positions (fractional, one cell)

Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.