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Crystal Lab › Prototype structures › Hexagonal

Ti₃Al₂N₂

Hexagonal · space group P63mc (No. 186) · Pearson hP22

Symmetry elements and Wyckoff positions (interactive)

Ti₃Al₂N₂ in P63mc

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

Unit cell

Lattice constants
a = 2.987 Å, b = 2.987 Å, c = 23.350 Å; α = 90.00°, β = 90.00°, γ = 120.00°
Cell volume
180.5 ų
Atoms in the conventional cell
22 (Al 4, Ti 10, N 8)
Formula units Z
2
Pearson symbol
hP22 — hexagonal / trigonal, primitive lattice, 22 atoms per conventional cell
Symmetry operations
12 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Al1Al2a20.00000.00000.1500
Ti2Ti2a20.00000.00000.3500
Al3Al2b20.33330.66670.2500
N4N2b20.33330.66670.6000
N5N2b20.33330.66670.9000
N6N2b20.33330.66670.1000
N7N2b20.33330.66670.4000
Ti8Ti2b20.33330.66670.0500
Ti9Ti2b20.33330.66670.4500
Ti10Ti2b20.33330.66670.5500
Ti11Ti2b20.33330.66670.9500

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 22 atoms drawn above are these sites multiplied by all 12 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

A2B4C5_hP22_186_ab_4b_a4b-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol hP22, then the space-group number 186, then the Wyckoff letters occupied by each element in turn (Al: 2a; Ti: 2a; Al: 2b; N: 2b; N: 2b; N: 2b; N: 2b; Ti: 2b; Ti: 2b; Ti: 2b; Ti: 2b). 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 A2B4C5_hP22_186_ab_4b_a4b-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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