## hexagonal graphite

https://doi.org/10.1351/goldbook.H02818
The thermodynamically @S05900@ form of @G02684@ with an ABAB stacking @ST06775@ of the @G02683@. The exact crystallographic description of this allotropic form is given by the space group $$d_{6h}^{4} - P6_{3}/\text{mmc}$$ (@U06562@ constants: $$a=245.6\ \mathrm{pm}$$, $$c=670.8\ \mathrm{pm}$$). Hexagonal @G02684@ is thermodynamically @S05900@ below approximately $$2600\ \text{K}$$ and $$6\ \text{GPa}$$.
Note:
The use of the term @G02684@ instead of the more exact term hexagonal @G02684@ may be tolerated in view of the minor importance of @R05385@, the other allotropic form.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 494 [Terms] [Paper]