Institute of Quantum Materials Science

Yekaterinburg, Russia

Institute of Quantum Materials Science

Yekaterinburg, Russia
SEARCH FILTERS
Time filter
Source Type

Gorbatov O.I.,Institute of Quantum Materials Science | Kuznetsov A.R.,RAS Institute of Metal Physics | Gornostyrev Yu.N.,RAS Institute of Metal Physics | Ruban A.V.,KTH Royal Institute of Technology | And 4 more authors.
Journal of Experimental and Theoretical Physics | Year: 2011

The formation of a short-range order in soft magnetic Fe-Si alloys depending on the annealing temperature has been investigated theoretically and experimentally. The B2-type short-range order has been observed in samples quenched from temperatures T > TC (where TC is the Curie temperature) with the content cSi close to the boundary of the two-phase region. Annealing at temperatures T < TC for the content c Si≥ 0.08 leads to an increase in the fraction of regions with the D03-type short-range order. The mechanism of the formation of the short-range order in Fe-Si solid solutions has been analyzed by the Monte Carlo simulation with the ab initio calculated interatomic interaction parameters. It has been shown that the energy of the effective Si-Si interaction in bcc iron strongly depends on the magnetic state of the matrix. As a result, the B2-type short-range order is formed at T > TC and is fixed at quenching, whereas the D03-type short-range order is equilibrium in the ferromagnetic state. The results reveal the decisive role of magnetism in the formation of the short-range order in Fe-Si alloys and allow the explanation of the observed structural features of the alloys depending on the composition and temperature. © 2011 Pleiades Publishing, Inc.


Gorbatov O.I.,Institute of Quantum Materials Science | Korzhavyi P.A.,KTH Royal Institute of Technology | Ruban A.V.,KTH Royal Institute of Technology | Johansson B.,KTH Royal Institute of Technology | Gornostyrev Yu.N.,RAS Institute of Metal Physics
Journal of Nuclear Materials | Year: 2011

Vacancy-solute interactions play a crucial role in diffusion-controlled processes, such as ordering or decomposition, which occur in alloys under heat treatment or under irradiation. Detailed knowledge of these interactions is important for predicting long-term behavior of nuclear materials (such as reactor steels and nuclear-waste containers) as well as for advancing our general understanding of kinetic processes in alloys. Using first-principles calculations based on the density functional theory and employing the locally self-consistent Green's function technique, we develop a database of vacancy-solute interactions in dilute alloys of bcc Fe with 3p (Al, Si, P, S), 3d (Sc-Cu), and 4d (Y-Ag) elements. Unrelaxed interactions within the first three coordination shells have been computed in the ferromagnetic state as well as in the paramagnetic (disordered local moment) state of the iron matrix. Magnetism is found to have a strong effect on the vacancy-solute interactions. Implications of the obtained results for interpreting the effects of vacancy trapping and enhanced impurity diffusion are discussed. © 2011 Elsevier B.V. All rights reserved.


Gorbatov O.I.,Institute of Quantum Materials Science | Korzhavyi P.A.,KTH Royal Institute of Technology | Ruban A.V.,KTH Royal Institute of Technology | Gornostyrev Y.N.,RAS Institute of Metal Physics
Solid State Phenomena | Year: 2011

Vacancy-solute interactions play a crucial role in diffusion-controlled phase transformations, such as ordering or decomposition, which occur in alloys under heat treatment or under irradiation. The knowledge of these interactions is important for predicting long-term behavior of nuclear materials (such as reactor steels and nuclear-waste containers) under irradiation, as well as for advancing our general understanding of kinetic processes in alloys. Using first-principles calculations based on density functional theory and employing the locally self-consistent Green's function technique, we develop a database of vacancy-solute interactions in dilute alloys of bcc Fe with 3p (Al, Si, P, S), 3d (Ti - Cu), and 4d (Nb - Ag) elements. Interactions within the first two coordination shells have been computed in the ferromagnetic state as well as in the paramagnetic (disordered local moment) state of the iron matrix. Magnetism is found to have a very strong effect on the vacancy-solute interactions. © (2011) Trans Tech Publications.


Gorbatov O.I.,Institute of Quantum Materials Science | Gornostyrev Y.N.,RAS Institute of Metal Physics | Kuznetsov A.R.,RAS Institute of Metal Physics | Ruban A.V.,KTH Royal Institute of Technology
Solid State Phenomena | Year: 2011

Short-range order formation in dilute Fe-Si and Fe-Al alloys has been investigated by statistical Monte Carlo simulations with effective interactions deduced from first principles calculations for different magnetic structures of bcc Fe. We find that the variation of the magnetic order from ferromagnetic to paramagnetic leads to significant changes in effective cluster interactions and, as follow, in short-range order parameters of alloys. It is shown in agreement with experiment the B2 type short-range order is formed above the Curie temperature, TC, while the D03 type short-range order is preferred below TC. © (2011) Trans Tech Publications.


Gorbatov O.I.,KTH Royal Institute of Technology | Okatov S.V.,Institute of Quantum Materials Science | Gornostyrev Yu.N.,RAS Institute of Metal Physics | Korzhavyi P.A.,KTH Royal Institute of Technology | Ruban A.V.,KTH Royal Institute of Technology
Physics of Metals and Metallography | Year: 2013

The methods of quantum-mechanical simulation have been used to study alloys of bcc iron with 3d transition metals in the ferromagnetic and paramagnetic states. It has been shown that the main factor that determines the solubility of the 3d elements is their electronic structure. The energy of the solution, mixing, and effective interatomic interactions vary regularly depending on the position of the element in the Periodic Table and on the magnetic state of the matrix. In some cases, depending on the magnetic state, changes in these quantities lead to the violation of the Hume-Rothery rules that determine the solubility of substitutional elements in alloys. The results obtained help us to understand the microscopic mechanisms that determine the solubility of alloying elements and their effect on the phase stability and structural state of steels. © 2013 Pleiades Publishing, Ltd.


Woods C.R.,University of Manchester | Britnell L.,University of Manchester | Eckmann A.,University of Manchester | Ma R.S.,University of Chinese Academy of Sciences | And 18 more authors.
Nature Physics | Year: 2014

When a crystal is subjected to a periodic potential, under certain circumstances it can adjust itself to follow the periodicity of the potential, resulting in a commensurate state. Of particular interest are topological defects between the two commensurate phases, such as solitons and domain walls. Here we report a commensurate-incommensurate transition for graphene on top of hexagonal boron nitride (hBN). Depending on the rotation angle between the lattices of the two crystals, graphene can either stretch to adapt to a slightly different hBN periodicity (for small angles, resulting in a commensurate state) or exhibit little adjustment (the incommensurate state). In the commensurate state, areas with matching lattice constants are separated by domain walls that accumulate the generated strain. Such soliton-like objects are not only of significant fundamental interest, but their presence could also explain recent experiments where electronic and optical properties of graphene-hBN heterostructures were observed to be considerably altered. © 2014 Macmillan Publishers Limited. All rights reserved.


Petrik M.V.,Ural Federal University | Gorbatov O.I.,Institute of Quantum Materials Science | Gornostyrev Y.N.,RAS Institute of Metal Physics
JETP Letters | Year: 2014

The formation of a short-range order in an Fe-Ga bcc alloy has been studied by Monte Carlo simulation with the use of effective interaction potentials calculated within the density functional theory for the ferromagnetic and paramagnetic states. It has been found that the pronounced short-range order of the D03 type is formed at Ga concentrations close to the boundary of the two-phase region at T < Tc, whereas no short-range order is observed at T < Tc. The results obtained are in agreement with the experimental X-ray diffraction analysis. The relation of the features of the short-range order in the Fe-Ga alloy to the magnetostriction value has been discussed. © 2013 Pleiades Publishing, Inc.


Petrik M.V.,Ural Federal University | Gorbatov O.I.,Institute of Quantum Materials Science | Gornostyrev Yu.N.,RAS Institute of Metal Physics
Physics of Metals and Metallography | Year: 2013

The method based on the density-functional theory has been used to study the solubility of 3p (Al, Si) and 4p (Ga, Ge) elements in ferromagnetic and paramagnetic states of bcc iron. To simulate the paramagnetic state, two different approaches have been employed, which were implemented using the SIESTA and LSGF packages. It has been established that the solution energy of all these impurities decreases upon the transition into the paramagnetic state. The solution energies obtained by averaging over the ensemble of unpolarized magnetic configurations agree well with the values obtained in the coherentpotential approximation. At the same time, the allowance for the magnetic polarization in the vicinity of an impurity leads to a decrease in the solution energy, which is most clearly pronounced at temperatures close to TC. The temperature dependence of the solution energies of the impurities in the paramagnetic state is discussed. © Pleiades Publishing, Ltd., 2013.


Akhukov M.A.,Radboud University Nijmegen | Fasolino A.,Radboud University Nijmegen | Gornostyrev Y.N.,Institute of Quantum Materials Science | Katsnelson M.I.,Radboud University Nijmegen
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Grain boundaries with dangling bonds (DBGB) in graphene are studied by atomistic Monte Carlo and molecular dynamics simulations in combination with density functional (siesta) calculations. The most stable configurations are selected and their structure is analyzed in terms of grain boundary dislocations. It is shown that the grain boundary dislocation with the core consisting of pentagon, octagon, and heptagon (5-8-7 defect) is a typical structural element of DBGB with relatively low energies. The electron energy spectrum and magnetic properties of the obtained DBGB are studied by density functional calculations. It is shown that the 5-8-7 defect is magnetic and that its magnetic moment survives after hydrogenation. The effects of hydrogenation and of out-of-plane deformations on the magnetic properties of DBGB are studied. © 2012 American Physical Society.


PubMed | Institute of Quantum Materials Science
Type: Journal Article | Journal: Physical chemistry chemical physics : PCCP | Year: 2015

Nanoscale inhomogeneities are typical for numerous metallic alloys and crucially important for their practical applications. At the same time, stabilization mechanisms of such a state are poorly understood. We present a general overview of the problem, together with a more detailed discussion of the prototype example, namely, Guinier-Preston zones in Al-based alloys. It is shown that coherent strain due to a misfit between inclusion and host crystal lattices plays a decisive role in the emergence of the inhomogeneous state. We suggest a model explaining the formation of ultrathin plates (with the thickness of a few lattice constants) typical for Al-Cu alloys. Discreteness of the array of misfit dislocations and long-ranged elastic interactions between them are the key ingredients of the model. This opens a way for a general understanding of the nature of (meta)stable embedded nanoparticles in practically important systems.

Loading Institute of Quantum Materials Science collaborators
Loading Institute of Quantum Materials Science collaborators