## Wikipedia - Graphite (en) Wikipedia - Графит (sr) Wikipedia - کربن (fa) Wikipedia - গ্রাফাইট (bn) Wikipedia - கடுங்கரி (ta) rhombohedral graphite

https://doi.org/10.1351/goldbook.R05385
A thermodynamically @[email protected] allotropic form of @[email protected] with an ABCABC stacking @[email protected] of the layers. The exact crystallographic description of this allotropic form is given by the space group $$D_{3\text{d}}^{5}- R\overline{3}m$$, (@[email protected] constants: $$a=256.6\ \mathrm{pm}$$, $$c=1006.2\ \mathrm{pm}$$).
Note:
The structure of rhombohedral @[email protected] can be best considered as an extended stacking fault in @[email protected] Rhombohedral @[email protected] can not be isolated in pure form (@[email protected] and laboratory preparations contain less than 40% of rhombohedral @[email protected] in combination with @[email protected]). It is produced by shear deformation of @[email protected] and transforms progressively to the hexagonal (ABAB) modification on heating above $$1600\ \text{K}$$.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 504 [Terms] [Paper]