Note: The term amorphous carbon is restricted to the description of carbon materials with localized π-electrons as described by P. W. Anderson (Phys. Rev., 1958, 109, 1492). Deviations in the C–C distances greater than 5% (i.e. $\frac{\mathrm{\Delta }x}{x_0}>0.05$, where $x_0$ is the inter-atomic distance in the crystal lattice for the ${\text{sp}}^2$ as well as for the ${\text{sp}}^2$ configuration) occur in such materials, as well as deviations in the bond angles because of the presence of 'dangling bonds'. The above description of amorphous carbon is not applicable to carbon materials with two-dimensional structural elements present in all pyrolysis residues of carbon compounds as polyaromatic layers with a nearly ideal interatomic distance of $a=142\text{pm}$ and an extension greater than $1000\text{pm}$.