Phenakite (Be₂SiO₄, S1₃)

Unit cell

Lattice constants

a = 12.440 Å, b = 12.440 Å, c = 8.231 Å; α = 90.00°, β = 90.00°, γ = 120.00°

Cell volume

1103.1 ų

Atoms in the conventional cell

126 (Be 36, O 72, Si 18)

Formula units Z

18

Pearson symbol

hR42 — hexagonal / trigonal, rhombohedral lattice, 42 atoms per conventional cell

Symmetry operations

18 per cell

Crystallographic sites

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 126 atoms drawn above are these sites multiplied by all 18 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

A2B4C_hR42_148_2f_4f_f-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol hR42, then the space-group number 148, then the Wyckoff letters occupied by each element in turn (Be: 18f; Be: 18f; O: 18f; O: 18f; O: 18f; O: 18f; Si: 18f). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

Li₂MoO₄, Li₂WO₄, LiZnPO₄, Zn₂SiO4 (willemite), (Zn, Mn)₂SiO₄ (troostite) <!--beginning with an

Note: S1₃, Phenakite.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B4C_hR42_148_2f_4f_f-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.