Electronic structure and chemical bond in naphthalene and anthracene

We investigated the electronic structure of crystalline naphthalene and anthracene within the framework of density functional theory including van der Waals interactions (DFT-D). It is established that for better agreement with experimental values it is necessary to use the increased values of the van der Waals radii, which is caused by an overestimated value of the van der Waals interactions in crystalline linear oligoacenes. Utilization of the DFT-D leads to a correct account of the dispersion forces, which results in a high precision of the computed lattice parameters and cohesive energy. Based on the relaxed crystal structures, we have computed the total and deformation electron density and determined the mechanism of chemical bonds formation in crystals of naphthalene and anthracene. It has been established that the chemical bond in molecular crystals is formed under the influence of not only intramolecular but also intermolecular interactions. On the basis of the Mulliken population analysis it was revealed that two C(3) atoms in naphthalene (or C(3) and C(4) in anthracene) have a positive charge and the population of the rest of the carbon atoms increased, as compared with isolated molecule.     

Determination of the kinetic strength constants and of the critical size of destruction of composite materials on the basis of recording of pulse electromagnetic radiation during their destruction

Kemerovo. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 153–159, July–August, 1994.     

Possibility of producing carbon mesoporous sorbents from coal raw materials

Porous carbon material from anthracite (2.5% of ash) produced at different activation temperatures with different burning degree is studied. According to the data of IR-spectroscopy and element analysis, oxidation results in the removal of aliphatic groups and the formation of oxygen-containing groups. Air oxidation causes formation of fractures, meso- and macropores.     

Interrelation of sorption properties and nanostructure of carbon molecular sieves from anthracites of Kuzbass

Main regularities in the formation of nanotexture and structure of carbon porous materials and development of pores in Kuzbass anthracites were considered. Basic principles of the production of carbon sorbents for efficient separation of gases such as methane and helium, hydrogen and carbon monoxide, were studied. Sorbents produced from Kuzbass coals were analyzed with the help of gas chromatography, SEM with element analyzer, sorpometry, and gas porometry. The literature data on the size of pores and associates of nanofragments were compared to the width of pores andsize of entrance windows in models of CMS (carbon molecular sieve) nanofragments, which were estimated with the help of quantum chemical modeling in MOPAC/PM-3 semiempirical program. The work resulted in the production of carbon molecular sieves for extraction of hydrogen from gas mixtures and in obtaining the data on the main characteristics of sorbents produced.     

Formation of radicals in stepwise thermolysis of polyunsaturated polycarbosilane —[(Me2SiC≡C)4Me2SiCH=CH] n —

The onset temperature of radical formation in the stepwise thermolysis of polyunsaturated polycarbosilane —[(Me₂SiCC)₄Me₂SiCH=CH] _n — with n > 2 was found by ESR spectroscopy. Beginning from 230°C two types of radicals are formed. The first radical arises on heating to 240°C due to the delocalization of unpaired electrons over the polyunsaturated polymer systems to H atoms of the Et groups of the polymer. The second radical appears at temperatures 240°C due to delocalization to H atoms of the Me groups through the vacant 3d-orbital of the Si atom.