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. ∆x/x0 > 0.05, where x₀ is the inter-atomic distance in the crystal lattice for the sp2 as well as for the sp2 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 @P04961@ residues of carbon compounds as polyaromatic layers with a nearly ideal interatomic distance of a = 142 pm and an extension greater than 1000 pm.