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Korobeynikov S.N.,Lavrentyev Institute of Hydrodynamics | Alyokhin V.V.,Lavrentyev Institute of Hydrodynamics | Annin B.D.,Lavrentyev Institute of Hydrodynamics | Babichev A.V.,Sobolev Institute of Geology and Mineralogy
Shell Structures: Theory and Applications - Proceedings of the 10th SSTA 2013 Conference | Year: 2014

To simulate the deformation and buckling of Single Layer Graphene Sheets (SLGSs), we use the molecular mechanics method. The matrices and vectors of the equations of motion of SLGSs were determined by a finite element technique, wherein the tangent stiffness matrix and the internal force vector of the nanostructure are obtained by assembling the matrices and vectors of the SLGS elements. In turn, the matrices and vectors of the elements of SLGSs are determined from generic N-body force field potentials of covalent interactions between carbon atoms. The DREIDING force field is considered. For this field, we use the elements of the twobody bond stretching potential energy and the three-body bond-angle bending potential energy. Furthermore, in the DREIDING force field, the four-body potentials corresponding to the bond torsion energy and the bond inversion energy are used. In addition to accounting for covalent forces, we consider the two-body van derWaals energy of the non-covalent interactions between carbon atoms. We have performed a computer simulation of the quasi-static deformation and buckling of a SLGS consisting of 464 carbon atoms. It has been shown that the quasi-static deformation of the compressed SLGS involves the Euler buckling mode of an elastic plate with one half-wave along the free edge of the sheet of the SLGS.

Sidorova O.V.,Paul Scherrer Institute | Sidorova O.V.,Russian Academy of Sciences | Saurer M.,Paul Scherrer Institute | Myglan V.S.,Siberian Federal University | And 10 more authors.
Climate Dynamics | Year: 2012

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ13C and δ18O in cellulose chronologies obtained for the period 1779-2007 and cell wall thickness (CWT) for 1900-2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ13C data contain a strong summer temperature signal, while δ18O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ13C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ18O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction. © 2011 Springer-Verlag.

News Article | February 15, 2017
Site: phys.org

But all bets are off, if the students journey to the center of the Earth, à la Jules Verne's Otto Lidenbrock or if they venture to one of the solar system's large planets, such as Jupiter or Saturn. "That's because extremely high pressure, like that found at the Earth's core or giant neighbors, completely alters helium's chemistry," says Boldyrev, faculty member in USU's Department of Chemistry and Biochemistry. It's a surprising finding, he says, because, on Earth, helium is a chemically inert and unreactive compound that eschews connections with other elements and compounds. The first of the noble gases, helium features an extremely stable, closed-shell electronic configuration, leaving no openings for connections. Further, Boldyrev's colleagues confirmed computationally and experimentally that sodium, never an earthly comrade to helium, readily bonds with the standoffish gas under high pressure to form the curious Na He compound. These findings were so unexpected, Boldyrev says, that he and colleagues struggled for more than two years to convince science reviewers and editors to publish their results. Persistence paid off. Boldyrev and his doctoral student Ivan Popov, as members of an international research group led by Artem Oganov of Stony Brook University, published the pioneering findings in the Feb. 6, 2017, issue of Nature Chemistry. Additional authors on the paper include researchers from China's Nankai University, Center for High Pressure Science and Technology, Chinese Academy of Sciences, Northwestern Polytechnical University, Xi'an and Nanjing University; Russia's Skolkovo Institute of Science and Technology, Moscow Institute of Physics and Technology, Sobolev Institute of Geology and Mineralogy and RUDN University; the Carnegie Institution of Washington, Lawrence Livermore National Laboratory, Italy's University of Milan, the University of Chicago and Germany's Aachen University and Photo Science DESY. Boldyrev and Popov's role in the project was to interpret a chemical bonding in the computational model developed by Oganov and the experimental results generated by Carnegie's Alexander Goncharov. Initially, the Na He compound was found to consist of Na cubes, of which half were occupied by helium atoms and half were empty. "Yet, when we performed chemical bonding analysis of these structures, we found each 'empty' cube actually contained an eight-center, two-electron bond," Boldyrev says. "This bond is what's responsible for the stability of this enchanting compound." Their findings advanced the research to another step. "As we explore the structure of this compound, we're deciphering how this bond occurs and we predicted that, adding oxygen, we could create a similar compound," Popov says. Such knowledge raises big questions about chemistry and how elements behave beyond the world we know. Questions, Boldyrev says, Earth's inhabitants need to keep in mind as they consider long-term space travel. "With the recent discovery of multiple exoplanets, we're reminded of the vastness of the universe," he says. "Our understanding of chemistry has to change and expand beyond the confines of our own planet." Explore further: Scientists discover extraordinary compounds that may be hidden inside Jupiter and Neptune More information: A stable compound of helium and sodium at high pressure, Nature Chemistry, DOI: 10.1038/nchem.2716

Romenskiy E.I.,RAS Sobolev Institute of Mathematics | Perepechko Y.V.,Sobolev Institute of Geology and Mineralogy | Reshetova G.V.,ICMMG
14th European Conference on the Mathematics of Oil Recovery 2014, ECMOR 2014 | Year: 2014

The new computational model for multiphase flow in deforming elastic porous media is proposed. The derivation of the model is based on the thermodynamically compatible hyperbolic systems of conservation laws theory. The flow of the mixture of compressible fluids in the elastic medium is supposed to be a continuum, in which the multiphase character of flow is taken into account. This phenomenological approach of continuum mechanics modelling allows us to formulate the system of governing equations in a divergent form, which is advantageous for the mathematical study of the different problems and for the development of advanced numerical methods. We present a thermodynamically compatible model for the flow of fluids mixture in elastic porous medium. The governing equations comprise balance laws for phase masses, total momentum and total energy supplemented by the equations for relative velocities in divergent form. The high accuracy Runge-Kutta-WENO numerical method for solving equations of the model is presened along the numerical test problem. The proposed model and developed numerical framework can be used in the wide range of oil recovery problems. Examples are: tracking oil/water interfaces in oil reservoirs, modeling of flows in the well surrounding formation.

Yaxley G.M.,Australian National University | Berry A.J.,Imperial College London | Kamenetsky V.S.,University of Tasmania | Woodland A.B.,Goethe University Frankfurt | Golovin A.V.,Sobolev Institute of Geology and Mineralogy
Lithos | Year: 2012

The Udachnaya East kimberlite sampled garnet peridotite xenoliths from a pressure range of 1.2 to 7.1GPa in the underlying Siberian cratonic lithosphere. Samples derived from <5.2GPa lie close to a typical cratonic geotherm of 40mWm -2, whereas more deeply derived samples have temperatures ≥100°C above this geotherm. Minor and trace element compositions of garnet and clinopyroxene indicate the presence of both depleted and metasomatically enriched material in the suite. Depleted material derives from the entire sampled depth interval, but enriched material is confined to pressures of 4.5 to 6.6GPa. Thus, the Siberian cratonic lithosphere under the Undachnaya pipe consisted of a relatively cool and depleted upper layer about 150km deep, underlain by a hotter layer which extended to at least 210km depth and contained both depleted and enriched material. Fe K-edge XANES was applied to garnets from this suite to measure their Fe 3+/∑Fe values, enabling determination of a redox profile through the lithospheric section represented by the xenolith suite. δlogO 2 [FMQ] varied from -2.5 to nearly -6.0 over the sampled pressure interval. An overall trend to lower δlogO 2 [FMQ] values with increasing pressure was defined mostly by the depleted samples. A superimposed oxidation trend to δlogO 2 [FMQ] values 1-2 units higher than the main trend mostly affected the deeper, enriched samples, indicating a clear link between metasomatism and oxidation. The amount of oxidation was insufficient to de-stabilize diamond in the deep lithosphere. A possible mechanism for metasomatic enrichment relates to localized, low degree "redox melting", whereby upwardly percolating CH 4±H 2O fluids would encounter progressively more oxidizing peridotite wall-rock resulting in diamond crystallization and increased water activity in the fluid. This could lead to local partial melting and enriched melts could migrate into cooler parts of the lithosphere and crystallize, thus enriching parts of the lithosphere. Melts thus formed are expected to be relatively enriched in Fe 3+ as it is moderately incompatible during partial melting. Lithospheric domains metasomatised by solidification of these melts would be relatively enriched in Fe 3+ and garnets may therefore have higher Fe 3+/∑Fe values, thus recording relatively higher δlogO 2 [FMQ] values. © 2012 Elsevier B.V.

Shatsky V.S.,RAS Institute of Geology and Mineralogy | Zedgenizov D.A.,Novosibirsk State University | Ragozin A.L.,Novosibirsk State University | Kalinina V.V.,Sobolev Institute of Geology and Mineralogy
European Journal of Mineralogy | Year: 2014

Diamonds from placer deposits in the northeastern Siberian platform were examined for variations in the isotopic composition of carbon and concentrations of nitrogen. The diamonds display large variability in N concentrations, ranging from below detection to 3500 ppm. Nitrogen levels in diamonds with eclogitic inclusions are generally high (average of 950 ppm) compared to diamonds of the ultramafic suite (average of 513 ppm). Diamonds belonging to variety V (classification scheme of Orlov, 1977) have relatively high N levels (from 1500 to 3500 ppm, average of 2549 ppm). The average nitrogen level is five times higher than the worldwide average. Values of δ13C in the diamonds range from -27.2 to -3% (n = 28) in eclogitic diamonds and from -7.1 to -0.5% (n = 16) in peridotitic diamonds. Diamonds of variety V range in δ13C from -24.1 to -17.4%. The distributions of nitrogen and its aggregation state in some diamond crystals imply the occurrence of multiple growth events. This is especially evident in the nitrogen content, which decreases and then increases from core to rim. The results indicate that there is no correlation between local variations in the isotopic composition of carbon and either the content or degree of aggregation of nitrogen. The diamonds of variety V differ from most diamonds worldwide in their high N content and light C-isotope composition. The large ranges of δ13C and the lack of correlation with nitrogen levels are inconsistent with the open-system Rayleigh isotopic fractionation of carbon species. The nature of the variations in the carbon isotope composition and the nitrogen concentrations indicate that the diamond growth medium had at least two sources of fluids/melts (mantle and recycled Earth crust via subduction). Mantle carbon was involved in the process of diamond formation during the final stages of diamond growth. © 013 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

Korobeynikov S.N.,Lavrentyev Institute of Hydrodynamics | Alyokhin V.V.,Lavrentyev Institute of Hydrodynamics | Babichev A.V.,Sobolev Institute of Geology and Mineralogy
Engineering Fracture Mechanics | Year: 2014

The molecular mechanics (MM) method based on the Modified Morse force field is used to determine the critical buckling parameters and post-critical deformation modes of single-walled carbon nanotubes (SWCNTs) twisted at the edges. Computer simulation of the buckling and post-critical deformation of nanotubes is performed using two versions of the MM method: the standard MM method and a mixed method combining the molecular mechanics and molecular structural mechanics approaches (MM/MSM method). Computer simulation shows that the MM/MSM method gives acceptable critical twisting angles, buckling modes, and post-critical deformed configurations of nanotubes, comparable to the critical twisting angles, modes, and configurations obtained using the standard MM method. More precisely, for the (10,. 10) armchair SCWNT 12.2919. nm long, the solutions obtained by both methods are similar up to the beginning of fracture of the SCWNT (at a twisting angle up to 240° for each edge), and for the (10,. 0) zigzag SCWNT 16.8980. nm long, the solutions obtained by both methods are similar up to the final twisting angle of 360° for each edge. The critical linear twisting angle for the (10,. 10) armchair SWCNT obtained in the present study is compared with the critical linear twisting angles obtained by other authors using the REBO, DREIDING, and MM3 force fields. It is concluded that the critical linear twisting angle obtained in the present study using the Modified Morse force field is unrealistically underestimated compared to the critical linear twisting angles obtained by other authors using the REBO, DREIDING, and MM3 force fields. © 2014 Elsevier Ltd.

Rashchenko S.V.,Novosibirsk State University | Likhacheva A.Y.,Sobolev Institute of Geology and Mineralogy | Bekker T.B.,Sobolev Institute of Geology and Mineralogy
High Pressure Research | Year: 2013

A new simplified synthesis of monocrystalline chips of SrB 4O7: Sm2+ pressure calibrant, well-suited for the diamond anvil cell (DAC) powder diffraction experiments, is proposed. It consists of ordinary solid-state synthesis of fine-grained SrB4O 7: Sm2+ and subsequent annealing near melting temperature. The obtained material was characterized and tested in HP-HT DAC experiment. © 2013 Taylor & Francis.

Korobeynikov S.N.,Lavrentyev Institute of Hydrodynamics | Alyokhin V.V.,Lavrentyev Institute of Hydrodynamics | Annin B.D.,Lavrentyev Institute of Hydrodynamics | Babichev A.V.,Sobolev Institute of Geology and Mineralogy
Archives of Mechanics | Year: 2012

Stubility/instability criteria of discrete elastic systems are used to study the buckling of nanostructures. The deformation of nanostructures is simulated by solving the nonlinear equations of molecular mechanics. The external forces applied to the nanostructure are assumed to be dead (that is the directions of their action remain constant throughout nanostructure deformation). We note that the positivedefiniteness property of the tangential stiffness matrix of a nanostructure is a universal sufficient stability criterion for both equilibrium states and quasi-static/dynamic motions of the nanostructure. The equilibrium configurations are stable in Lyapunov's sense, and quasi-static/dynamic motions are stable in a finite time interval t ∈ (0, T cr) in which the positive-definiteness property of this matrix is preserved. For dynamic motions of nanostructures, the stability property in this time interval follows from Lee's criterion of quasi-bifurcation of solutions of second order ODEs. The nonpositive definiteness of the tangential stiffness matrix of nanostructures at a time t > T cr corresponds to both unstable equilibrium configurations and unstable dynamic motions. Computer procedures for determining the critical time and buckling mode(s) are developed using this criterion and are implemented in the PIONER FE code. This code is used to obtain new solutions for the deformation and buckling of twisted (10, 10) armchair and (10,0) zigzag single-walled carbon nanotubes. © 2012 by IPPT PAN.

Korobeynikov S.N.,Lavrentyev Institute of Hydrodynamics | Alyokhin V.V.,Lavrentyev Institute of Hydrodynamics | Annin B.D.,Lavrentyev Institute of Hydrodynamics | Babichev A.V.,Sobolev Institute of Geology and Mineralogy
Mathematics and Mechanics of Solids | Year: 2015

This paper presents a quasi-static nonlinear buckling analysis of compressed single-layer graphene sheets (SLGSs) using the molecular mechanics method. Bonded interactions between carbon atoms are simulated using a modified parameter set of the DREIDING force field that leads to better agreement between simulated mechanical properties of graphene and reference literature data than the standard parameter set of this force field (see Mayo et al., J Phys Chem 1990; 94: 8897-8909). Identification of constraints of atoms of the SLGS edges with the boundary conditions of clamped and simply supported thin plates is made. The buckling loads and modes obtained by linear and nonlinear buckling analysis of a compressed quadratic SLGS with a side length of 6€‰nm are shown to be close to each other. In addition, it has been found by nonlinear buckling analysis that only equilibrium configurations with modes of initial post-buckling deformed configurations correlated with the one-half-wave column-like buckling mode have stable equilibrium configurations for clamped and simply supported SLGSs. As the edges of a simply supported SLGS approach each other, the geometry of this mode of post-buckling deformation with inclusion of the non-bonded van der Waals (vdW) interactions between carbon atoms becomes closer to the geometry of a single-walled carbon nanotube, and without inclusion of the vdW interactions, this mode has the geometry of a cylinder with a drop-shaped cross-section. © SAGE Publications.

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