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Yanilkin A.V.,All Russia Research Institute of Automatics
High Temperature | Year: 2017

The thermodynamic properties of α-phase and liquid uranium have been investigated by the method of quantum molecular dynamics. The isotherms and equilibrium properties (pressure, temperature, and internal energy) along isochores and isotherms have been calculated for densities of 16.5–41.1 g/cm3 and temperatures up to 60000 K. The dependence of the thermal pressure on temperature and internal energy is analyzed. The melting boundary of α-phase uranium is estimated. The shock adiabat is calculated for pressures up to 1.5 TPa based on the equation of state derived here. The results obtained are in good agreement with the published experimental data and the results of calculations according to different theoretical models. © 2017, Pleiades Publishing, Ltd.

Igashov S.Yu.,All Russia Research Institute of Automatics | Tchuvil'sky Yu.M.,Moscow State University
EPJ Web of Conferences | Year: 2012

Algebraic version of the orthogonality conditions model is developed by analogy with the algebraic version of the resonating group model. It is shown that all exchange terms excluding ones originated by the exchange kernel of the potential energy can be easily taken into account in the frame of the formalism of the version. The potential term as a whole is modelled phenomenologically. Both direct algebraic approach and the method basing on the solution of the integro-differential Schrödinger equation containing nonlocal terms related to the forbidden and the semi-forbidden states are proposed. This equation turns out to be preferable in studies of narrow resonances. It is demonstrated that decay width of a system into two-heavy-fragment channel is strongly affected by the nonlocal terms. © Owned by the authors 2012.

Shmelev D.L.,Russian Academy of Sciences | Barengolts S.A.,RAS A.M. Prokhorov General Physics Institute | Shchitov N.N.,All Russia Research Institute of Automatics
Technical Physics Letters | Year: 2014

We propose a model for determining the influence of the relative content of deuterium in a zirconium cathode on the properties of vacuum-arc plasma. It is shown that the occlusion of deuterium in the cathode leads to an additional energy consumption for its ionization and to the related decrease in the average charge of cathode material ions in the discharge plasma. Deuterium in the cathode spot is fully ionized, and the drift velocity of deuterium ions almost coincides with that of ions of the cathode material. © 2014, Pleiades Publishing, Ltd.

Kuksin A.Y.,All Russia Research Institute of Automatics | Rokhmanenkov A.S.,RAS Joint Institute for High Temperatures | Stegailov V.V.,Moscow Institute of Physics and Technology
Physics of the Solid State | Year: 2013

The solution energy of H and He in various interstitial and substitution positions in the hcp lattice of α-Ti has been calculated based on the method of electron density functional. The lowest solution energy of He corresponds to the basal octahedral position and that of H corresponds to the octahedral position (next in energy is the tetrahedral position). The calculated vibration frequencies of H in various positions are used for identification of lines in the vibration spectrum obtained by the method of neutron inelastic scattering. Taking into account these spectra, it can be concluded that hydrogen atoms occupy in the hcp lattice of Ti both the octahedral and tetrahedral positions even at 600 K. The available experimental data do not contradict the conclusion that the octahedral position is more preferable in α-Ti. The energy barriers are estimated for various diffusion paths of H and He. © 2013 Pleiades Publishing, Ltd.

Malygin G.A.,RAS Ioffe Physical - Technical Institute | Ogarkov S.L.,All Russia Research Institute of Automatics | Andriyash A.V.,All Russia Research Institute of Automatics
Physics of the Solid State | Year: 2014

The mechanism of formation of a cellular dislocation structure in face-centered cubic (fcc) metal crystals subjected to shock compression at strain rates Ε̇ > 106 s-1 has been considered theoretically within the dislocation kinetic approach based on the kinetic equation for the dislocation density (dislocation constitutive equation). A dislocation structure of the cellular type is formed in the case of a two-wave structure of the compression wave behind its shock front (elastic precursor). It has been found that, at pressures σ > 10 GPa, the dislocation cell size Λc depends on the pressure σ and the density ρG of geometrically necessary dislocations generated at the shock front according to the relationship Λc ∼ ρG -n ∼ σ-m, where n = 1/4-1/2, m = 3/4-3/2, and m = 1, for different pressures and orientations of the crystal. It has been shown that, in copper and nickel crystals with the shock loading axis oriented along the [001] direction, the cellular structure is not formed after reaching the critical pressures σc equal to 31 and 45 GPa, respectively. © 2014 Pleiades Publishing, Ltd.

Romashka M.Y.,All Russia Research Institute of Automatics | Yanilkin A.V.,All Russia Research Institute of Automatics
Physics of Metals and Metallography | Year: 2014

A procedure for the simulation of the low-temperature stage of annealing of irradiated α iron is suggested. Based on the method of molecular dynamics, the reaction rate constants and the energies of activation for the recombination of Frenkel pairs are calculated. For the simulation of the ID and IE stages, the coefficient of diffusion of interstitials is calculated. The calculations are performed for three different potentials of interaction of iron atoms. All three potentials give close results for the majority of the configurations of Frenkel pairs considered. A comparison of the calculated annealing curve with the experimental curve of the stage I is given. Based on this comparison, a correspondence between different configurations of close Frenkel pairs and peaks of the experimental curve has been established. It is shown that one peak can be associated with several configurations of close pairs. © 2014, Pleiades Publishing, Ltd.

Petrov Y.V.,Russian Academy of Sciences | Inogamov N.A.,Russian Academy of Sciences | Migdal K.P.,All Russia Research Institute of Automatics
JETP Letters | Year: 2013

The two-temperature (Te > Ti) thermal conductivity coefficient κ2T and electron-ion heat transfer coefficient α, which are necessary for the quantitative description of the processes initiated by ultrashort laser pulse, have been calculated using a kinetic equation, the matrix element for the scattering probability, and a screened Coulomb potential describing the interaction between charged particles. Quantitative information has been obtained for coefficients κ2T and α values for noble and transition metals, where the d-band electrons play a significant role. © 2013 Pleiades Publishing, Ltd.

Malygin G.A.,RAS Ioffe Physical - Technical Institute | Ogarkov S.L.,All Russia Research Institute of Automatics | Andriyash A.V.,All Russia Research Institute of Automatics
Physics of the Solid State | Year: 2014

The influence of the structure factors (sizes of grains and precipitates) on the dislocation structure formed in polycrystals and alloys behind the shock wave front (elastic precursor) has been theoretically discussed in terms of the dislocation kinetic relationships and kinetic equation for the dislocation density. The critical conditions of the transition from the cellular dislocation structure to a uniform dislocation distribution have been formulated. These conditions are used to determine the dependences of the critical pressure, above which the dislocation distribution becomes uniform, on the grain size and precipitate volume density. © 2014, Pleiades Publishing, Ltd.

Novoselov I.I.,Moscow Institute of Physics and Technology | Kuksin A.Y.,Moscow Institute of Physics and Technology | Yanilkin A.V.,All Russia Research Institute of Automatics
Physics of the Solid State | Year: 2014

The diffusion coefficients of vacancies and interstitials along symmetrical tilt grain boundaries in molybdenum have been calculated using the molecular dynamics method. The migration energies of defects have been obtained. The activation energy and coefficients of grain boundary self-diffusion have been deter-mined. A comparison of the obtained results with the studies of other authors indicates that boundaries formed between particles in the powder in sintering experiments have a higher diffusion activity as compared to stable grain boundaries in polycrystals. © 2014 Pleiades Publishing, Ltd.

Kosov M.,All Russia Research Institute of Automatics | Savin D.,All Russia Research Institute of Automatics
Journal of Physics: Conference Series | Year: 2015

The CHIPS-TPT physics library for simulation of neutron-nuclear reactions on the new exclusive level is being developed in CFAR VNIIA. The exclusive modeling conserves energy, momentum and quantum numbers in each neutron-nuclear interaction. The CHIPS-TPT algorithms are based on the exclusive CHIPS library, which is compatible with Geant4. Special CHIPS-TPT physics lists in the Geant4 format are provided. The calculation time for an exclusive CHIPS-TPT simulation is comparable to the time of the corresponding Geant4- HP simulation. In addition to the reduction of the deposited energy fluctuations, which is a consequence of the energy conservation, the CHIPS-TPT libraries provide a possibility of simulation of the secondary particles correlation, e.g. secondary gammas, and of the Doppler broadening of gamma lines in the spectrum, which can be measured by germanium detectors. © Published under licence by IOP Publishing Ltd.

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