Papers by Abdiravuf Dzhurakhalov
Physical Review B, 2008
ABSTRACT Recently, core-shell Ag-Co, Ag-Cu, and "onionlike" Cu-Co equilibrium c... more ABSTRACT Recently, core-shell Ag-Co, Ag-Cu, and "onionlike" Cu-Co equilibrium configurations were predicted in the case of isolated face centered cubic (fcc) bimetallic clusters, and three shell onionlike configurations were predicted in the case of ternary metallic clusters with spherical and truncated octahedral morphologies. In the present paper, immiscible binary CuCo and ternary AgCuCo clusters with icosahedral structures are studied as functions of their size and composition. Clusters studied are formed by 13, 55, 147, 309, and 561 atoms corresponding to the five smallest possible closed shell icosahedral structures. An embedded atom model potential is used to describe their cohesion. Equilibrium configurations are investigated by means of Metropolis Monte Carlo free energy minimization in the (NPT) canonical ensemble. Most simulations are achieved at 10 and 300 K. The effect of temperature on segregation ordering is systematically investigated. Selected cases are used to identify the effect of size and composition on melting. In contrast with fcc clusters, homogeneous onionlike configurations of binary clusters are not predicted. When it is allowed by the composition, a complete outer shell is formed by Cu in binary Cu-Co clusters and by Ag in ternary Ag-Cu-Co clusters. Depending on temperature, Co may precipitate into decahedral groups under the Cu vertices of the icosahedra in binary clusters, while the Co-Cu configuration in ternary clusters drastically depends on the Ag coating. Despite the multicomponent character of the clusters and the immiscibility of the species forming them, for most compositions and sizes, equilibrium structures remain close to perfectly icosahedral at 10 K as well as at 300 K.
IOP Conference Series: Materials Science and Engineering, 2015
ABSTRACT The specific peculiarities of 0.5-10 keV Ne+, Ar+, Kr+, Be+ and Se+ ions scattering, spu... more ABSTRACT The specific peculiarities of 0.5-10 keV Ne+, Ar+, Kr+, Be+ and Se+ ions scattering, sputtering and implantation processes at grazing ion bombardment of GaAs (001), Si(001), SiC(001) and Cu(100) surfaces and their possible application for the surface modification and analysis have been studied by computer simulation. Sputtering yields in the primary knock-on recoil atoms reghne versus the initial energy of incident ions (E0 = 0.5-5 keV) and angle of incidence (ψ = 0-30°) counted from a target surface have been calculated. The colliding particles mass ratio influence on the energy losses of scattering particles, sputtering yields and near-surface depth distributions of implanted particles is established, ft was shown that in the case of grazing ion bombardment the layer-by-layer sputtering is possible and its optimum are observed within the small angle range of the glancing angles near the threshold sputtering angle. Comparative studies of layer-by-layer sputtering for Si(001) and SiC(001) surfaces versus the initial energy of incident ions as well as an effective sputtering and sputtering threshold are discussed.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998
A computer simulation method has been used to study small angle correlated scattering of low ener... more A computer simulation method has been used to study small angle correlated scattering of low energy ions by a single crystal surface with submonolayer adsorption coverages. It has been shown that a rainbow effect and a chain effect at multiple scattering on adsorbate and substrate atoms and inverse ratio of masses of colliding particles lead to the appearance of additional peaks in angular and energy distributions.
Journal of Physics: Conference Series, 2015
The recently developed simulation framework VirtualLeaf uses Metropolis Monte Carlo dynamics for ... more The recently developed simulation framework VirtualLeaf uses Metropolis Monte Carlo dynamics for studying plant tissue morphogenesis. Minimizing the energy of the tissue is done by an energy evaluation-only method. We developed a more robust criterion for the energy minimization method for the multivariable and complex systems where the use of a gradient norm is impossible. The proposed criterion is based on checking energy changes in a sliding window of successive energy steps against a threshold value. The advantages of the sliding window criterion are discussed and results obtained by this method are presented. The impact of the choice threshold value on the energy minimization has been studied.
Modelling and simulation are increasingly used as tools in the study of plant growth and developm... more Modelling and simulation are increasingly used as tools in the study of plant growth and developmental processes. By formulating experimentally obtained knowledge as a system of interacting mathematical equations, it becomes feasible for biologists to gain a mechanistic understanding of the complex behaviour of biological systems. In this review, the modelling tools that are currently available and the progress that has been made to model plant development, based on experimental knowledge, are described. In terms of implementation, it is argued that, for the modelling of plant organ growth, the cellular level should form the cornerstone. It integrates the output of molecular regulatory networks to two processes, cell division and cell expansion, that drive growth and development of the organ. In turn, these cellular processes are controlled at the molecular level by hormone signalling. Therefore, combining a cellular modelling framework with regulatory modules for the regulation of cell division, expansion, and hormone signalling could form the basis of a functional organ growth simulation model. The current state of progress towards this aim is that the regulation of the cell cycle and hormone transport have been modelled extensively and these modules could be integrated. However, much less progress has been made on the modelling of cell expansion, which urgently needs to be addressed. A limitation of the current generation models is that they are largely qualitative. The possibilities to characterize existing and future models more quantitatively will be discussed. Together with experimental methods to measure crucial model parameters, these modelling techniques provide a basis to develop a Systems Biology approach to gain a fundamental insight into the relationship between gene function and whole organ behaviour.
The peculiarities of sputtering processes at 0.5-5 keV Ne grazing ion bom-bardment of Si(001) and... more The peculiarities of sputtering processes at 0.5-5 keV Ne grazing ion bom-bardment of Si(001) and SiC(001) surfaces and their possible application for the surface modification have been studied by computer simulation. Sputtering yields in the primary knock-on recoil atoms regime versus the initial energy of incident ions (E 0 = 0.5-5 keV) and angle of incidence (ψ = 0-30 •) counted from a target surface have been calculated. Comparative studies of layer-by-layer sputtering for Si(001) and SiC(001) surfaces versus the initial energy of incident ions as well as an effective sputtering and sputtering threshold are discussed.
The realized possibility of layer-by-layer removal of atom layers from the surface of sample unde... more The realized possibility of layer-by-layer removal of atom layers from the surface of sample under grazing ion bombardment is of great importance for preparation of a clean surface of crystals, as well as for development of methods of their diagnostics based on layer-by-layer analysis. Until the ion-impact desorption processes of molecules, especially their orientation dependencies were insufficiently investigated both experimentally and theoretically. In this report the energetic and angular distributions of sputtered Ag atoms and desorbed oxygen atoms and molecules at grazing 5-10 keV H ¡ , N ¡ , Ne ¡ ions bombardment of the clean and O 2 covered Ag(110) surfaces have been presented. The interactions of 5-10 keV H ¡ , N ¡ , Ne ¡ ions with both clean and O 2 covered Ag surface at grazing incidence have been simulated by using the binary collision approximation method. The particle interactions were described by the screened Coulomb potential with the Ziegler-Biersack-Littmark approximation to the Thomas-Fermi screening function. The inelastic energy losses were considered as local and calculated by modified Firsov model with their including into the scattering kinematics. The sputtering has been simulated in the primary knock-on regime. Only the primary knock-on recoil atoms ejected from first, second and third layers have been considered. The presence of a planar potential energy barrier for Ag atoms and oxygen molecules on the surface was taken into account. Some details of this binary code with repulsive potentials and its fitness for describing of ion scattering have been described in [1]. The energetic and angular distributions of sputtered and desorbed particles versus the initial energy and mass of bombardment ions have been calculated. The formation of such distributions and the dynamics of change of their shapes are discussed.
The characteristics of the low-angle multiple scattering of heavy ions of medium energies by the ... more The characteristics of the low-angle multiple scattering of heavy ions of medium energies by the single-crystal surface of YBa2Cu3O(7-x) ceramic were investigated by using a computer simulation. The possibilities afforded by the ion scattering method for the diagnostics and monitoring of the local composition, structure, and condition of the surfaces of complex compounds are demonstrated.
The mechanical properties of the cell wall play an important role in cell growth, water relations... more The mechanical properties of the cell wall play an important role in cell growth, water relations, tissue mechanics and other aspects of plant development. To better describe the cell wall mechanics we used a viscoelastic model based on Maxwell elements in which the deformation of wall is determined by the combination of Hooke's law and Newton's law. This model implemented in the VirtualLeaf software framework describes the balance between turgor pressure and cell wall resistance by an elastic energy and pressure potential energy of the system. In this new approach the rest length (which corresponds to the length in the absence of turgor pressure) of each wall element and the turgor pressure in each cell are updated by solving an ordinary differential equation. As the whole dynamic process of the system includes cell growth and cell division accompanied by formation of new walls, wall elements and cells, significant modifications and extensions have been made to VirtualLeaf.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
The ion scattering and sputtering processes at low energy grazing N + and Ne + ion bombardment of... more The ion scattering and sputtering processes at low energy grazing N + and Ne + ion bombardment of clean and oxygen covered Ag(1 1 0) surface have been investigated by computer simulation in the binary collision approximation.
Materials Science and Engineering: B, 2003
The CoSi 2 , NiSi 2 , NaSi 2 and BaSi 2 thin epitaxial films have been obtained by molecular beam... more The CoSi 2 , NiSi 2 , NaSi 2 and BaSi 2 thin epitaxial films have been obtained by molecular beam epitaxy and ion implantation. The growth mechanisms as well as the composition, electron and crystalline structure of these films were studied and determinate. It was shown that NiSi 2 , CoSi 2 , BaSi 2 and NaSi 2 epitaxial films crystallise as cubic lattice, and the bond between atoms of metal and Si has ionic-covalent nature. It was determined that the metal silicide films are heterostructure relatively Si and their width band gap make up 0.5 Á/0.7 eV. #
ABSTRACT A comparative study of 1-5 keV P+ ions channeling in thin (dZ=5OOÅ) and thick Si(110), S... more ABSTRACT A comparative study of 1-5 keV P+ ions channeling in thin (dZ=5OOÅ) and thick Si(110), SiC(110), GaP(110) and AsGa(110) crystals has been carried out by computer simulation within binary collision approximation. The ion ranges, energy losses, angular and energy distributions, as well as depth profile distribution have been calculated. It was shown that for paraxial part of a beam the main contribution to the total energy losses comes from inelastic ones. It has been established that energy and depth profile distributions depend on width of channel in the direction and mass of target atoms.
Surface Science, 1999
Molecular oxygen adsorbed on an Ag(110) surface has been studied by computer simulation of low en... more Molecular oxygen adsorbed on an Ag(110) surface has been studied by computer simulation of low energy ion scattering. The lying-down adsorptions of molecular oxygen with an orientation of its molecular axis along the 110 azimuth on an Ag(110) surface were been simulated. The energy distributions and the behaviour of the scattering loops of scattered He+, N+ and Ne+ ions have been presented. It was shown that the behaviour of the scattering loops gives the possibility to determine the location of adsorbed molecules on the surface. The development of the proposed technique would allow an estimate of its feasibilities.
MRS Proceedings, 2005
ABSTRACT The ion sputtering and implantation into GaAs(001) surface at 1-5 keV Se+ grazing ion bo... more ABSTRACT The ion sputtering and implantation into GaAs(001) surface at 1-5 keV Se+ grazing ion bombardment have been investigated by computer simulation.The azimuth angular dependencies of sputtering and penetration yield at grazing incidence have been calculated. It was observed that these dependencies correlate the crystal orientation. The depth distributions of 1-5 keV Se ions implanted into GaAs(001) for several azimuth angles of incidence have been presented.
2000 International Conference on Ion Implantation Technology Proceedings. Ion Implantation Technology - 2000 (Cat. No.00EX432), 2000
The dechanneling of ions from the monoatomic steps on the GaP(100) surface as well as the traject... more The dechanneling of ions from the monoatomic steps on the GaP(100) surface as well as the trajectories of these particles have been carefully studied. The energy and angular distributions of the dechanneling ions have been calculated. It was shown that the dechanneling ions form the characteristic peaks in the angular and energy distributions of scattered ions
2000 International Conference on Ion Implantation Technology Proceedings. Ion Implantation Technology - 2000 (Cat. No.00EX432), 2000
ABSTRACT The peculiarities of ion implantation into the one-component and binary crystal surface ... more ABSTRACT The peculiarities of ion implantation into the one-component and binary crystal surface under conditions of low-energy ion bombardment at grazing incidence have been investigated by computer simulation. The depth distributions of 5 keV Ar ions implanted into Cu(001) surface and 1 keV Be and Se ions implanted into GaAs(001) for a range of grazing angles of incidence (3-30°) have been calculated and presented
Vacuum, 1993
... _'U7 II 97>). IS ilcnskv and FS l'arilis. 7Jr Tech h1.,.4R, 171 I 1I... more ... _'U7 II 97>). IS ilcnskv and FS l'arilis. 7Jr Tech h1.,.4R, 171 I 1IlJ7h1_ FF Umarov et al: Spatial extension a ES Parilis, N Yu Turaev, FF Umarov and SL Nizhnayja, Theorv of Scattering of the Medium Energy Atoms by the Solid Surface, pp 212. FAN, Tashkent (1987). ...
The Journal of Physical Chemistry C, 2010
The phase transition processes induced by ultrashort, 100 fs pulsed laser irradiation of Au, Cu, ... more The phase transition processes induced by ultrashort, 100 fs pulsed laser irradiation of Au, Cu, and Ni are studied by means of a combined atomistic-continuum approach. A moderately low absorbed laser fluence range, from 200 to 600 J/m 2 is considered to study phase transitions by means of a local and a nonlocal order parameter. At low laser fluences, the occurrence of layer-by-layer evaporation has been observed, which suggests a direct solid to vapor transition. The calculated amount of molten material remains very limited under the conditions studied, especially for Ni. Therefore, our results show that a kinetic equation that describes a direct solid to vapor transition might be the best approach to model laser-induced phase transitions by continuum models. Furthermore, the results provide more insight into the applicability of analytical superheating theories that were implemented in continuum models and help the understanding of nonequilibrium phase transitions. † Part of the "Barbara J. Garrison Festschrift".
Surface Review and Letters, 1997
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Papers by Abdiravuf Dzhurakhalov