The suggested approach "Selected set of samples + selected set of analytical tools" occurred quite efficient when applying to sp 2 amorphous carbons, thus providing a transformation of 'amorphous' representation of the issue, based on particulars, into a 'crystalline' one based on a limited set of fixed commonalities. The slogan first part implies a set of different-origin solid samples. The second part concerns analytical tools, the most suitable to achieve the goal. The parts combining means the application of each tool to the whole set of samples. In the current study, two natural sp 2 amorphous carbons, namely, shungite carbon and antraxolite, as well as two engineered products -carbon blacks CB632 and CB624, all of the four bodies belonging to the elitist highest-carbon-content sp 2 species, were subjected to analytical study by using modern structural and compositional analytical techniques. The approach has allowed disclosing the following steady points that are common to the whole class of this carbon allotrope and that may lay the foundation of consolidate, more 'crystalline' representation of what are sp 2 amorphous carbons:1. sp 2 Amorphous carbons are products of particular chemical reactions related to their basic structural units. Further macroscopic agglomeration of the latter plays a subsidiary role. 2. The units represent framed graphene molecules of 1-2 nm and 1-x*10 (x=1-3) nm in size in the case of natural and engineered products, respectively.3. Framing of graphene molecules, predominantly incomplete with respect to the number of vacant places, concerns only edge atoms and is implemented by the related chemical additives, such as hydrogen, oxygen, nitrogen, sulfur and halogens which are attached to the carbon core via chemical bonding. 4. The molecules small size provides a countable number of newly formed chemical bonds.INS and XPS allow attributing the bonds to chemical compositions restricted by number while QCh ensures reliable support. 5. Temperature and pressure as well as physical state and chemical content of surrounding media are the main factors governing geochemistry and technical chemistry of carbon products. 6. Graphene molecules, laying the foundation of sp 2 amorphous carbons, are strongly radicalized due to which the latter acquire a new facet in the space of their properties, being the largest repository of stable radicals.

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The standard D-G-2D pattern of Raman spectra of sp2 amorphous carbons is considered from the viewpoint of graphene domains presenting their basic structure units (BSUs) in terms of molecular spectroscopy. The molecular approximation allows connecting the characteristic D-G doublet spectra image of one-phonon spectra with a considerable dispersion of the C=C bond lengths within graphene domains, governed by size, heteroatom necklace of BSUs as well as BSUs packing. The interpretation of 2D two-phonon spectra reveals a particular role of electrical anharmonicity in the spectra formation and attributes this effect to a high degree of the electron density delocalization in graphene domains. A size-stimulated transition from molecular to quasi-particle phonon consideration of Raman spectra was experimentally traced, which allowed evaluation of a free path of optical phonons in graphene crystal.

Neutron powder diffraction and inelastic neutron scattering (INS) were used to determine the structure and hydrogen content of basic structure units (BSUs) of sp2 amorphous carbons at the atomic level. A comparative study of two natural (shungite carbon and antraxolite) and two synthetic (carbon blacks) species of the highest-rank carbonization revealed nanosize stack structure of all samples. The stacks are formed by BSUs representing framed graphene molecules (graphene oxyhydrides) of ∼2.5 nm lateral dimension. The INS study showed the presence of hydrogen atoms in the BSU framing area as well as of adsorbed water in the sample pores configured by BSU stacks. Simulated INS spectra of adsorbed water showed its monolayer disposition within the pores. BSU INS spectra were simulated for a set of particular models simulating H-standard features of the INS spectra of graphene-based species, in general, and BSU hydrogen component of the studied samples, in particular. Simulations were performed in the framework of both spin-independent (density functional theory) and spin-dependent (unrestricted Hartree–Fock) molecular vibrational dynamics. The obtained results allowed a reliable presentation of the hydrogeneous component of the BSU atomic structure and proposing a specific INS classification of sp2 amorphous carbons with respect to their hydrogeneousness.

Two-mode valence electron configuration of carbon atoms lays the foundation of the unique two-mode amorphous state of the monoatomic carbon solid. From the fundamentals of solid-state physics, sp 3 and sp 2 amorphous carbons are two different amorphous species characterized by conceptually different short-range orders, namely, groups of tetrahedrally bonded sp 3 configured atoms and nanoscale size-restricted sp 2 graphene domains framed with heteroatom necklaces. Molecular character of sp 2 amorphics is coherent with the reaction mechanism of the solid amorphicity in due course of the enforced fragmentation.

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