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Information × Registration Number 0203U008003, 0101U002782 , R & D reports Title The theoretical modelling of chemical composition of atmosphere of substars and the interstar substance popup.stage_title Head Pedash Ju.F., Registration Date 02-04-2003 Organization Kharkov National University named after V.N.Karazin popup.description2 Subject: chemical and ionization equilibria in atmospheres of substars at low temperatures. Goal of work: to compute chemical equilibrium abundances of gaseous mixtures typical in elemental composition for conditions on the surface of brown dwarf, to elucidate peculiarities in chemical and ionization equilibria in steady-state conditions, and following model evolution track. Method of investigation: statistical mechanics and thermodynamics of multicomponent systems, numerical algorithms of quantum chemistry and chemical equilibria. Implicitly iterative method of Gauss-Seidel family in Cruise version is implemented and applied to chemical equilibrium problem in atmospheres of brown dwarfs. The Cruise method is best suited to compute equilibrium abundances in the system "large reservoir (H,He) - minor additives" (C,N,O). General polylinear type of response was found between the results of Newtonian and Cruise methods. Iterations by ionic strength are realized within Cruise method, with allowance for finite Coulomb energy/thermal energy ratio. The resulting algorithm was applied to gaseous system H-He-C-N-O of solar elemental abundances at the T = 3000 to 500 K, r = 10-4 to 10-2 g/cm3. Carbon chemistry was found to depend heavily on the Oxygen content in the system; in particular, CH4 and CO become most abundant species instead of С2H2 and HCN in carbon-rich envelopes. Positive charge in the system H-He-C-N-O at low temperatures is mostly carried by complex cations NH4+·HY, Y = OH, NH2. The chemical abundance changes, beginning from the age of ca. 107 years, are mostly due to the changes in temperature. With Lithium species in mind, theoretical studies are also made to develop technique of Coupled Cluster approach in multidimensional model space. As a decisive step toward CCSDTQ, algorithmic diagram operations within CC theory are introduced. Large extent of convergence acceleration has been achieved in CC procedures due to rational spin-orbit space partition, and due to DIIS. Area of use: Gas-phase chemicalequilibria in stellar and planetary atmospheres. Basic processes of chemical technology, MGD techniques, harmful waste utilization. Product Description popup.authors popup.nrat_date 2020-04-02 Close