A. A. Kuzubov

Contact-induced spin polarization in graphene/h-BN/Ni nanocomposites

Atomic and electronic structure of graphene/Ni(111), h-BN/Ni(111) and graphene/h-BN/Ni(111) nanocomposites with different numbers of graphene and h-BN layers and in different mutual arrangements of graphene/Ni and h-BN/Ni at the interfaces was studied using LDA/PBC/PW technique. Using the same technique corresponding graphene, h-BN and graphene/h-BN structures without the Ni plate were calculated for the sake of comparison. It was suggested that C-top:C-fcc and N-top:B-fcc configurations are energetically favorable for the graphene/Ni and h-BN/Ni interfaces, respectively. The Ni plate was found to induce a significant degree of spin polarization in graphene and h-BN through exchange interactions of the electronic states located on different fragments.

Theoretical study of the magnetic properties of ordered vacancies in 2D hexagonal structures: Graphene, 2D-SiC, and h-BN

The magnetic properties of vacancies in 2D hexagonal structures—graphene and 2D-SiC and h-BN monolayers—have been studied. It has been found that a local magnetic moment exists in all listed systems in the presence of vacancies. However, in 2D hexagonal silicon carbide, the local magnetic moment appears only in the presence of silicon vacancy. In addition, the effect of the distance between vacancies in a monolayer on transitions between the ferromagnetic and antiferromagnetic states has been revealed.

Theoretical study of the diffusion of lithium in crystalline and amorphous silicon

The effect of the lattice deformation on potential barriers for the motion of a lithium atom in crystalline silicon has been studied through ab initio density functional calculations. A new universal method of calculating the diffusion coefficient of an admixture in amorphous solid media through the activation mechanism has been proposed on the basis of these data. The method is based on the calculation of the statistical distribution of potential barriers for the motion of an admixture atom between minima depending on the position of neighboring atoms. First, the amorphous structure, which is generated by annealing from the crystalline structure with vacancies, has been simulated. Then, the statistical distribution of the potential barriers in the amorphous structure for various local environments of the admixture atoms has been calculated by means of linear regression with the parameters determined for barriers in crystalline silicon subjected to different deformations. The diffusion coefficient of the admixture has been calculated from this distribution by using the Arrhenius formula. This method has been tested by the example of crystalline and amorphous silicon with admixture of lithium atoms. The method demonstrates that the diffusion of lithium in amorphous silicon is much faster than that in crystalline silicon; this relation is confirmed experimentally.

Mobility of vacancies under deformation and their effect on the elastic properties of graphene

The effect of isolated vacancies on the elastic properties of a graphene sheet has been investigated by the ab initio density functional method. An almost inverse linear dependence of the Young’s modulus on the concentration of vacancies has been revealed. The height of potential barriers for the motion of vacancies in various directions has been calculated as a function of various independent applied strains. The velocity of vacancies at various temperatures has been calculated as a function of applied strains using the transition state theory.

A theoretical study of lithium absorption in amorphous and crystalline silicon

Lithium absorption in silicon is studied at the DFT level. By means of the developed method of modeling the structure of amorphous silicon, including with impurities, it is shown that with an increase in the lithium concentration intermediate amorphous LixSiy phases, up to the crystalline Li15Si4 phase, form in crystalline silicon. An increase in the silicon cell volume, as it is filled with lithium, is calculated. A nonlinear dependence of silicon voltage on lithium intercalation is found. The lithium diffusion coefficient in crystalline silicon at a low lithium concentration is calculated and it is demonstrated for amorphous silicon that lithium diffusion is substantially accelerated by the lattice deformation inherent in amorphous silicon. The calculated values can be used in the production of high-capacity lithium ion batteries with a silicon anode.

Theoretical study of vacancies and adatoms in white graphene

The stability of the B and N atomic vacancies and divacancies in an h-BN monolayer deformed by 2 and 4% along one of the axes has been investigated. It has been established that the N atomic vacancies are most stable; their concentration is insignificant and does not affect the properties of white graphene. The number of vacancies depends on the mobility of N and B atoms on the layer surface; therefore, the probability of recombination with the vacancies has been estimated. It has been revealed that the energy barrier for the migration of the B and N adatoms is about 0.23 and 1.23 eV, respectively. In view of such a low barrier for the B adatom, this type of adatoms will quite rapidly move over the surface and recombine with vacancies, in contrast to the N adatoms. Therefore, only nitrogen atom vacancies can exist in the h-BN monolayer grown by the methods, where the adatoms could possibly appear on the surface.

Density-functional theory study of the electronic structure of thin Si ∕ Si O 2 quantum nanodots and nanowires

The atomic and electronic structures of a set of proposed pentagonal thin (

Contact-induced spin polarization in BNNT(CNT)/TM (TM=Co, Ni) nanocomposites

1.6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}

The effect of halogen substitution on the structure and electronic spectra of fluorone dyes

in diameter) silicon/silica quantum nanodots (QDs) and nanowires (NWs) with narrow interface, as well as parent metastable silicon structures (

Analysis of hydrogen adsorption in the bulk and on the surface of magnesium nanoparticles

1.2\phantom{\rule{0.3em}{0ex}}\mathrm{nm}