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APPLICATIONS: Theoretical Physics

The computer simulation of physical and chemical properties of carbon-based nanostructures and study nature of superhardness.

Antipina Liubov
Technological Institute for Superhard and Novel Carbon Materials

DRIVER: 1. Modeling of 3D quasi-amorphous material, carbon nanocomposites consisting of diamond nanoclusters or polymeric fullerene as two extreme cases and surrounded by a matrix of sp3- hybridized carbon. 2 . Study of the influence of various factors such as the degree of compactness, size, density and structure of the fullerene polymer, the size of the surrounding matrix, the matrix type (crystalline diamond , sp3-hybridized amorphous carbon) , data on the stiffness of nanocomposites . 3 . Mechanical properties of pure graphene and graphene with defects ( mono-and divacancies , Stone- Wales defects , dislocations , etc.) , depending on its stiffness coefficient of the concentration and type of defects.

STRATEGY: Using direct ab-initio methods is very difficult for large systems containing more than 500 atoms in the structure . Therefore, in solving the problems will be applied as specialized methods for the study of polyatomic structures - the method of empirical potentials Brenner . This potential describes the elastic mechanical properties and the dependence of the lattice dynamics of these structures on the temperature for systems containing thousands of atoms on good level. For small structures containing less 1000 atoms will also be applied quantum- mechanical methods to describe the proposed models . Small structures will be described in the electron density functional theory (DFT) using the functionals LDA ( local electron density approximation ), GGA ( generalized gradient approximation method ) and some of its generalizations. DFT method allows to obtain various properties of crystals with good accuracy. Thus , the error in the calculation of the atomic geometry of the material is usually about 1%. Electron and phonon spectra of crystals are also reproduced with high accuracy , which confirms the comparison of the experimental and theoretical data . For the calculation of systems that can easily be represented in the form of periodic structures will be used packages VASP and Siesta. Non-periodic structure with a large number of atoms ( such as individual graphene or diamond clusters) will be described from first principles using the fragmented approach of molecular orbitals (FMO) allows to evaluate the structural and mechanical properties of systems with high electron localization . This method has been successfully applied to describe the nanostructures with dimensions of a few tens of nanometers. Will also be the method of density functional theory in the strong-coupling scheme (DFTB), allowing to obtain structural and mechanical data on periodic and aperiodic structures with good accuracy.

OBJECTIVE: Development of new approaches to the study of nature of superhardness of carbon nanomaterials embedded within the structure of nanoscale defects or nanoclusters various sizes and prediction of new structures with unique properties using methods of computer modeling.

IMPACT: Prediction of nanostructures with unique properties that can be used in various fields of engineering, military and aerospace industry. Fundamental research into the nature superhardness nanomaterials.

USAGE: Superhard materials (diamond, CBN , etc.) have a special place in modern science and technology . Unique hardness and wear resistance , high thermal conductivity , transparency and speed of the charge carriers do diamond virtually indispensable material for many industrial sectors: the processing nodes spacecraft made of superhard materials, as the supporting stones in marine chronometers , differing particularly precise way, in other precision navigation instruments , metallurgy , defense industry , in research. Moreover , a variety of cutting and drilling tools such as drill bits , reamers , countersinks with diamond coatings have longer life , are faster cutting and finishing better than conventional carbide inserts of tungsten carbide tool . It was emphasized that the application of CVD- diamond coating thickness of 15-25 microns of tools for turning, drilling, milling increase their efficiency in the processing of titanium alloys, aluminum alloys , composites.

AREA: Condensed Matter Physics, Theoretical Physics, Physical Chemistry

Chrage transfer processes in proton-helium collisions

Galstian Alexander
Moscow State Uiversity

DRIVER: In collaboration with German experimentalists a row of articles on charge transfer processes in proton-helium collisions was prepared for publication. In these collisions helium ion can appear in different quantum states. Different wave function models and perturbations theory approximations are discussed, including the second Born one.

STRATEGY: Cross section evaluation using Born approximation.

OBJECTIVE: Explanation of the experimental data using different process mechanisms; different mechanism’s contribution to the cross section evaluation.

IMPACT: t is shown that the scattering of the backward emitted electrons with small scattering angles arises almost due to shake-off processes. The first Born approximation with helium wave function with strong electron-electron correlations is quite good to understand the scattering of electrons backward, but is insufficient to explain the forward scattering.

USAGE: Atomic ionization

AREA: Theoretical Physics, Mathematics

Theoretical investigation of different carbon nanostructures

Demin Victor
Emanuel Institute of Biochemical Physics of RAS

DRIVER: Investigation of structures which consist of nanotubes and fullerenes, quantum dots on graphene-graphane nanoribbons: geometry and electronic properties

STRATEGY: Problems are solved with the use of software packages that implement the methods of molecular mechanics and DFT

OBJECTIVE: Purpose - definition of dependence of electronic, mechanical and other properties of the geometry of the carbon structure

IMPACT: The results can be used to facilitate the experimental materials with desired properties

USAGE: Synthesis of the studied materials can be useful in different areas of our lives. The nanotube-fullerenes structures are promising materials for the solar industry. Quantum dots on a graphene-graphane nanoribbons can be used in electronic devices, so they have forbidden zone, in contrast to pure graphene

AREA: Physical Chemistry, Theoretical Physics

Calculations of structure in LC droplets

Rudiak Vladimir
Moscow State Uiversity

DRIVER: Development of a method for calculating nematic and cholesteric liquid crystals in a droplet of any shape with any boundary conditions and under magnetic field

STRATEGY: We apply Monte-Carlo technique to a simple lattice model taking into account elastic deformations, interaction with surface and magnetic field, and disclination energy

OBJECTIVE: Develop a method and a software for LC structure calculations in droplets

IMPACT: The ability to calculate LC structure in microdroplets allows to optimize droplet structure for a certain demands such as electiooptical devices based on PDLC materials

USAGE: Liquid crystal physics, display technologies

AREA: Theoretical Physics, Condensed Matter Physics