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The use of symmetry-adapted linear combinations (SALC) of atomic orbitals in large unit cell (LUC) calculations of solids is considered. A procedure is proposed of SALC generation being convenient for the automation in computer calculations. It is shown that the use of the SALC in the semiempirical LUC calculations has advantages in essential computer time and memory savings and in simple distinction of the infinite crystal band states from the molecular orbitals obtained.

It is shown that the use of the simple cubature formula for the approximate calculation of the density matrix em in the non-local Hartree-Bock exchange for crystals leads to a non-physical divergence of the lattice sums. To overcome this difficulty it is proposed to introduce a weight function in the cubature formula for the numerical integration over the Brillouin zone in calculating non-local exchange. It is discussed the simple way t o choose the nodes of the numerical integration which is based on the large unit cell transformation in the direct and reciprocal lattices. This choice allows to extend the special point technique of the Brillouin zone integration to the non-local exchange calculation. pacxonHMocTn B pelueTosHbIx cyMMax 06MeHHOfi XIacTM n o~e~u~a n a XapTpH-cDoHa.

The energy band structure of corundum is investigated theoretically using the semiempirical Mulliken-Rddenberg method. A crystal potential is constructed basing on the self-consistent effective atomic charges and electronic populations obtained within the framework of the method used. The connection of thc energy bands with the atomic states of thc constituent atoms is discussed. The valence band widths and the electronic density distribution appear to be in good agreement with experimental data.

The use of the deterministic model of chain growth for the copolymerization of vinylidene fluo ride and hexafluoropropene instead of the classical Markov model makes it possible to correctly relate the data of the 19 F NMR spectra of copolymers with different compositions to the mechanism of formation of macromolecules. The possible mechanism of copolymerization in the proposed model description involves the coordination of the radical center of the growing chain on the double bond of a monomer with subsequent incorporation of the monomer unit into the polymer chain. Although the proposed model disregards the ori entation of monomer units along the chain, it properly describes the experimental data and provides an idea of the alternation of units in the copolymer at different copolymer compositions.

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This article discusses application of 3D laser scanning aimed at assessment of consequences of destructions resulted from fires and other technogenic disasters of oil and gas facilities. Deformations of structures and equipment as a consequence of emergencies sometimes cannot be detected visually. It is required to apply modern instrumentation to determine deviations from designed parameters. In addition, after disasters it is required to determine the scope of loss and faults of equipment. Application of 3D laser scanning makes it possible to estimate both availability of buildings and equipment for further operation and the scope of destructions at complex engineering facilities of oil and gas industry. Laser scanning makes it possible to reduce significantly time required for examination and data processing in comparison with other measurement methods.

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