Term: rhombohedral graphite
https://doi.org/10.1351/goldbook.R05385

Definition:
A thermodynamically unstable allotropic form of graphite with an ABCABC stacking sequence of the layers. The exact crystallographic description of this allotropic form is given by the space group D3d5 - R3(bar)m, (unit cell constants: a = 256.6 pm, c = 1006.2 pm).

Note: The structure of rhombohedral @G02684@ can be best considered as an extended stacking fault in @H02818@. Rhombohedral @G02684@ can not be isolated in pure form (@N04088@ and laboratory preparations contain less than 40% of rhombohedral @G02684@ in combination with @H02818@). It is produced by shear deformation of @H02818@ and transforms progressively to the hexagonal (ABAB) modification on heating above 1600 K.

Related Terms:
1) graphite (http://doi.org/10.1351/goldbook.G02684).
2) hexagonal graphite (http://doi.org/10.1351/goldbook.H02818).
3) unstable (http://doi.org/10.1351/goldbook.U06569).
4) sequence (http://doi.org/10.1351/goldbook.ST06775).
5) unit cell (http://doi.org/10.1351/goldbook.U06562).
6) natural graphite (http://doi.org/10.1351/goldbook.N04088).

Source: PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 504 (https://doi.org/10.1351/pac199567030473)

Citation: 'rhombohedral graphite' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.R05385

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