Bertrandite (Be₄Si₂O₇(OH)₂, S4₆)

Unit cell

Lattice constants

a = 8.713 Å, b = 15.268 Å, c = 4.568 Å; α = 90.00°, β = 90.00°, γ = 90.00°

Cell volume

607.8 ų

Atoms in the conventional cell

60 (O 36, Be 16, Si 8)

Formula units Z

4

Pearson symbol

oC60 — orthorhombic, base-centred lattice, 60 atoms per conventional cell

Symmetry operations

8 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 60 atoms drawn above are these sites multiplied by all 8 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

A4B7C2D2_oC60_36_2b_a3b_2a_b-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC60, then the space-group number 36, then the Wyckoff letters occupied by each element in turn (O: 4a; O: 4a; O: 4a; Be: 8b; Be: 8b; O: 8b; O: 8b; O: 8b; Si: 8b). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Note: S4₆, Bertrandite.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A4B7C2D2_oC60_36_2b_a3b_2a_b-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.