High multiplicity states in disordered carbon systems: Ab initio and semiempirical study

Quantum Chemical Simulation of Phenol-Formaldehyde Resin Carbonization in the Presence of Phosphoric Acid: Computational Evidence of Michaelis–Arbuzov-Type Reaction

“…Analogously to previously described carbon cluster, obtained by dehydrogenization of styrene-divinylbenzene copolymer, 18,19 PhF-derived carbon clusters have close low-lying high-multiplicity states as a quasi-degenerate ground state (Figure 3a, Supplement A in the Supporting Information). Therefore, according to straightforward atomistic simulation, the PhF resin carbonization results in disordered structure with preorganized curved graphene sheets having nonsinglet electronic ground states.…”

“…Analogously to previously described carbon cluster, obtained by dehydrogenization of styrene-divinylbenzene copolymer, , PhF-derived carbon clusters have close low-lying high-multiplicity states as a quasi-degenerate ground state (Figure a, Supplement A in the Supporting Information).…”

“…This article reports a semiempirical quantum-chemical (QC) simulation of the carbonization of neat and H 3 PO 4 -impregnated PhF resins to reveal the elementary acts responsible for chemical bonding of P-containing groups to the backbone of AC, very analogously to the previous works on carbonization of poly(styrene-divinylbenzene) , and poly(vinylpyridine-divinylbenzene) copolymers, and following the ideas recently proposed based on ReaxFF simulation of the phenolic and polyacrylonitrile resins. In contrast with the traditional approach, where AC structure is reduced to the ensemble of graphite-like nanoparticles − (thus reducing the surface chemistry of AC to the chemistry of graphene edge), we investigated the transformations of the polymer chains, which lead to disordered postpolymeric motives.…”

“…In contrast with the traditional approach, where AC structure is reduced to the ensemble of graphite-like nanoparticles − (thus reducing the surface chemistry of AC to the chemistry of graphene edge), we investigated the transformations of the polymer chains, which lead to disordered postpolymeric motives. As previously demonstrated, , such structures often possess a polyradical character due to abundance of unsaturated carbon atoms, defining inconvenient properties of carbonizate and leading to reactions traditionally considered as exotic for organic chemistry. Therefore, different spin multiplicity states have been considered for the carbon clusters upon carbonization.…”

Density Functional Theory versus Complete Active Space Self-Consistent Field Investigation of the Half-Metallic Character of Graphite-Like and Amorphous Carbon Nanoparticles

“…A recent quantum chemical investigation has demonstrated that both graphite-like and amorphous model clusters of carbon possess a set of pseudodegenerate spin states, conferring them half-metallic properties. − The number of these pseudodegenerate spin states depends on the quantity of unsaturated carbene-like sites conjugated via graphitic or cumulenic bridges. Such features should have a tremendous effect on the physicochemical properties of carbon nanoparticles. − Previous calculations based on density functional theory (DFT) suggest that the electronic structures of carbon clusters possess significant multiconfigurational character, as reflected in the large extent of spin contamination .…”