ИСТИНА

In our nonempirical studies, several kinds of carbon-based systems were considered and different problems were shown to be solved based on the results obtained. These are model carbon particles of nanodiamond, mixed diamond–graphite or diamond–geodesic polyarene, and fullerene types. Structural properties of individual particles, their interaction with each other, and probable surface modification upon the interaction with water were analyzed. The systems selected enabled us to follow structural peculiarities and reactivities of surface sites depending on the local σ/π-balance in the electron binding, formal unsaturated valences of atoms, and their close neighborhoods. Relative probabilities of the surface modification with different functional groups, the resulting local hydrophobicity/hydrophilicity of surface segments, and the character of interaction between different typical sites of carbon-based particles that results in the formation of clusters or aggregates stabilized by either covalent or van-der-Waals intermolecular bonds were considered. Model systems involved 20 to 250 carbon atoms and up to 35 water molecules. Calculations were carried out either at the density functional level with exchange-correlation functionals of B3LYP or PBE0 type and Gaussian basis sets, which involved polarization and in some cases diffuse functions on the nuclei. When interactions were expected to be of dispersion kind, calculations were carried out with the use of DFT-D approach with the explicit inclusion of dispersion corrections in modified DFT-D3 variant. Whenever possible, more accurate energy estimates were obtained in the second order of the Moeller-Plesset perturbation theory. Calculations were carried out with the use of PC GAMESS and Firefly 8.0 program packages on Chebyshev supercomputer of the Supercomputing Center of Lomonosov Moscow State University.