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Rhombohedral: R 3 m (No. 166) 105 (rh.) 315 (hex.) Partly due to its complexity, whether this structure is the ground state of Boron has not been fully settled. α-As: A7: Rhombohedral: R 3 m (No. 166) 2 (rh.) 6 (hex.) in grey metallic form, each As atom has 3 neighbours in the same sheet at 251.7pm; 3 in adjacent sheet at 312.0 pm. [18]
However, the rhombohedral axes are often shown (for the rhombohedral lattice) in textbooks because this cell reveals the 3 m symmetry of the crystal lattice. The rhombohedral unit cell for the hexagonal Bravais lattice is the D-centered [ 1 ] cell, consisting of two additional lattice points which occupy one body diagonal of the unit cell with ...
In monoclinic, trigonal, tetragonal, and hexagonal systems there is one unique axis (sometimes called the principal axis) which has higher rotational symmetry than the other two axes. The basal plane is the plane perpendicular to the principal axis in these crystal systems.
If the crystal system is trigonal, then the lattice system is hexagonal unless the space group is one of the seven in the rhombohedral lattice system consisting of the 7 trigonal space groups in the table above whose name begins with R. (The term rhombohedral system is also sometimes used as an alternative name for the whole trigonal system.)
Pages in category "Chemical elements with rhombohedral structure" The following 6 pages are in this category, out of 6 total. This list may not reflect recent changes .
It can be used to define the rhombohedral lattice system, a honeycomb with rhombohedral cells. A rhombohedron has two opposite apices at which all face angles are equal; a prolate rhombohedron has this common angle acute, and an oblate rhombohedron has an obtuse angle at these vertices.
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Stibarsen has the same crystal structure as arsenic and antimony, with the intermediate values of the lattice parameters. This structure (space group R 3 m No. 166) is variably described as hexagonal, trigonal and rhombohedral because of the overlap between these terms (see trigonal crystal system).