Virtual Vibrational Analytics of Reduced Graphene Oxide.

The digital twin concept lays the foundation of the virtual vibrational analytics suggested in the current paper. The latter presents extended virtual experiments aimed at determining the specific features of the optical spectra of the studied molecules that provide reliable express analysis of the body spatial structure and chemical content. Reduced graphene oxide was selected as the virtual experiment goal. A set of nanosize necklaced graphene molecules, based on the same graphene domain but differing by the necklace contents, were selected as the relevant DTs. As shown, the Raman spectra signatures contained information concerning the spatial structure of the graphene domains, while the molecule necklaces were responsible for the IR spectra. Suggested sets of general frequency kits facilitate the detailed chemical analysis. Express analysis of a shungite carbon, composed of rGO basic structural units, revealed the high ability of the approach.

Graphene Domain Signature of Raman Spectra of sp2 Amorphous Carbons.

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.

Molecular theory of graphene oxide.

Applied to graphene oxide, the molecular theory of graphene considers its oxide as a final product in the succession of polyderivatives related to a series of oxidation reactions involving different oxidants. The graphene oxide structure is created in the course of a stepwise computational synthesis of polyoxides of the (5,5) nanographene molecule governed by an algorithm that takes into account the molecule's natural radicalization due to the correlation of its odd electrons, the extremely strong influence of the structure on properties, and a sharp response of the molecule behavior on small actions of external factors. Taking these together, the theory has allowed for a clear, transparent and understandable explanation of the hot points of graphene oxide chemistry and suggesting reliable models of both chemically produced and chemically reduced graphene oxides.

Odd-electron molecular theory of graphene hydrogenation.

This paper highlights the molecular essence of graphene and presents its hydrogenation from the viewpoint of the odd-electron molecular theory. This chemical transformation was performed computationally, using a particular algorithm, through the stepwise addition of either hydrogen molecules or hydrogen atoms to a pristine graphene molecule. The graphene was considered to be a membrane, such that either both sides or just one side of the membrane was accessible to adsorbate, and the atoms on the perimeter of the membrane were either fixed (fixed membrane) or free to move (free-standing membrane). The algorithm explored the spatial distribution of the number of effectively unpaired electrons N (DA) over the carbon skeleton of the molecule. The highest ranked N (DA) values were considered to indicate the target atoms at each reaction step. The dependence of the hydrogenation itself and the final graphene hydrides on external factors such as whether the membrane was fixed, if both sides or only one side of the membrane were accessible to hydrogen, and whether the hydrogen was in the molecular or atomic state. Complete hydrogenation followed by the formation of a regular chairlike graphane structure (CH)(n) was only found to be possible for a fixed pristine graphene membrane for which the basal plane is accessible to hydrogen atoms from both sides.

A tricotage-like failure of nanographene.

The response of a nanographene sheet to external stresses was considered in terms of a mechanochemical reaction. The quantum chemical realization of the approach was based on the coordinate-of-reaction concept for the purpose of introducing a mechanochemical internal coordinate (MIC) that specifies a deformational mode. The related force of response is calculated as the energy gradient along the MIC, while the atomic configuration is optimized over all of the other coordinates under the MIC constant-pitch elongation. The approach is applied to the benzene molecule and (5,5) nanographene. A drastic anisotropy in the microscopic behavior of both objects under elongation along a MIC was observed when the MIC was oriented either along or normally to the C-C bond chain. Both the anisotropy and the high stiffness of the nanographene originate from the response of the benzenoid unit to stress.