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Crystal Lab › Prototype structures › Orthorhombic

Nb₄As₃

Orthorhombic · space group Cmcm (No. 63) · Pearson oC56

Symmetry elements and Wyckoff positions (interactive)

Nb₄As₃ in Cmcm

Setting
Loading the group…
x = 0.10, y = 0.17, z = 0.08

Unit cell

Lattice constants
a = 3.516 Å, b = 14.660 Å, c = 18.830 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
970.6 ų
Atoms in the conventional cell
56 (Nb 32, As 24)
Formula units Z
8
Pearson symbol
oC56 — orthorhombic, base-centred lattice, 56 atoms per conventional cell
Symmetry operations
16 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Nb5Nb4a40.00000.00000.0000
As1As4c40.00000.30760.2500
As2As4c40.00000.58790.2500
Nb6Nb4c40.00000.94680.2500
As3As8f80.00000.09820.8821
As4As8f80.00000.15770.0772
Nb7Nb8f80.00000.26240.8382
Nb8Nb8f80.00000.46620.8800
Nb9Nb8f80.00000.33180.0285

The multiplicity and the Wyckoff letter say how many copies of the site the group makes in one cell and on which kind of symmetry element the site sits; the 56 atoms drawn above are these sites multiplied by all 16 operations. Press Wyckoff under Colour to see the sites, and tick a symmetry element on the left to see which atoms lie on it.

How to read the label

A3B4_oC56_63_2c2f_ac3f-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC56, then the space-group number 63, then the Wyckoff letters occupied by each element in turn (Nb: 4a; As: 4c; As: 4c; Nb: 4c; As: 8f; As: 8f; Nb: 8f; Nb: 8f; Nb: 8f). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A3B4_oC56_63_2c2f_ac3f-001 (M. J. Mehl et al., Comput. Mater. Sci. 136, S1 (2017); D. Hicks et al., ibid. 161, S1 (2019) and 199, 110450 (2021); S. Eckert et al., ibid. 240, 112988 (2024)). Symmetry elements, Wyckoff assignment and the diagram are computed on this page from the group operations.

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