In crystallography, the rhombohedral (or trigonal) crystal system is one of the seven lattice point groups, named after the two-dimensional rhombus. A crystal system is described by three basis vectors. In the rhombohedral system, the crystal is described by vectors of equal length, of which all three are not mutually orthogonal. The rhombohedral system can be thought of as the cubic system stretched diagonally along a body. a = b = c; . In some classification schemes, the rhombohedral system is grouped into a larger hexagonal system.
There exists only one rhombohedral Bravais lattice.
|rhombohedral holohedral||D3d||calcite, corundum, hematite|
|rhombohedral hemimorphic||C3v||tourmaline, alunite|
|rhombohedral tetartohedral||S6||dolomite, ilmenite|
|rhombohedral tetartohedral||C3||none verified|
Ambiguities in powder indexing: conjunction of a ternary and binary lattice metric singularity in the cubic system.
Nov 01, 2004; A lattice metric singularity occurs when unit cells defining two (or more) lattices yield the identical set of unique calculated...