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1
Content available remote Surface diffusion and cluster formation of gold on the silicon (111)
Plechystyy V., Shtablavyi I., Rybacki K., Winczewski S., Mudry S., Rybicki J.
Journal of Achievements in Materials and Manufacturing Engineering
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2020
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Vol. 101, nr 2
49--59
EN
Purpose: Investigation of the gold atoms behaviour on the surface of silicon by molecular dynamics simulation method. The studies were performed for the case of one, two and four atoms, as well as incomplete and complete filling of gold atoms on the silicon surface. Design/methodology/approach: Investigations were performed by the method of molecular dynamics simulation using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). MEAM potential of interatomic interaction was used for modelling. Molecular dynamic simulations were carried out in isothermal-isobaric ensemble (NpT) with a timestep 1.0 fs. Findings: As a result of studies, the preferred interaction between gold atoms and the formation of clusters at temperatures up to 800 K was revealed. Analysis of the temperature dependences of the number of large jumps of atoms made it possible to calculate the activation energy of a single jump. It was found that activation energy of single atomic displacement decreases with increasing number of gold atoms. Research limitations/implications: Only a limited number of sets of atoms were used in the study. It is possible that for another combination of atoms and a larger substrate surface, the formation of gold nanoislands on the silicon surface can be observed, which requires further research. Practical implications: The research results can be used to select the modes of gold sputtering to create gold nanoislands or nanopillars on the silicon surface. Originality/value: Computer modelling of the behaviour of gold atoms on the surface of silicon with the possibility of their self-organization and cluster formation was performed for the first time.
2
Content available remote Improvements to the two-phase sandwich method for calculating the melting points of pure metals
Rybacki K., Winczewski S., Pleechystyy V., Rybicki J.
Computational Methods in Science and Technology
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2019
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Vol. 25, No. 2
105--116
EN
The thermophysical properties of metal alloys are often investigated via molecular dynamics (MD) simulations. An exact and reliable estimation of the thermophysical parameters from the MD data requires a properly and carefully elaborated methodology. In this paper, an improved two-phase sandwich method for the determination of the metal melting temperature is proposed, based on the solid-liquid equilibrium theory. The new method was successfully implemented using the LAMMPS software and the C++11 Standard Libraries and then applied to aluminum and copper systems. The results show that the proposed procedure allows more precise calculations of the melting temperature than the widely used onephase boundary methods.
3
Content available remote Projekt stanowiska badawczego do testowania mikro i nano-skrawania w warunkach próżni i niskich temperatur
Musiał W., Dziedzic J., Rybicki J., Kordowska M.
Mechanik
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2014
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R. 87, nr 2CD
PL
Rozwój informatyki w ostatnich kilku dekadach umożliwił intensyfikację obliczeń komputerowych na poziomie molekularnym. Modelowanie zjawisk fizycznych przy pomocy komputera umożliwiło weryfikację i nowe podejście do wiedzy teoretycznej dotyczącej praw fizyki i umożliwiło ich analizę na poziomie atomowym. Współcześnie symulacje komputerowe używane są nie tylko do sprawdzania i weryfikowania teorii naukowych, ale również aby przewidywać wyniki eksperymentów i umożliwiać opisywanie i identyfikowanie modeli rzeczywistych procesów. Modele molekularne umożliwiają wykorzystywanie symulacji również do analizy skrawania w nanoskali.
EN
The last several decades have witnessed the flourishing and maturing of computer simulation. Modelling physical phenomena by means of a computer has acquired a status of a discipline in its own right, along the age-old theoretical and empirical approaches. Today, simulation is used not only to validate the predictions of theory and the results of experiment, it also has predictive capacity of its own, describing the exact behavior of simplified models of actual systems. Low cost and relative simplicity constitute major advantages of the simulation approach over experimental analysis when nanoscale systems are considered.
4
Content available remote Modelowanie molekularne w procesach mikro i nano obróbki
Musiał W., Rybicki J, Białoskórski M., Kordowska M.
Mechanik
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2013
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R. 86, nr 2CD
PL
W artykule przedstawiono możliwości realizacji symulacji molekularnych w odniesieniu do procesów nano i mikro wygładzania powierzchni obrabianych. Zaprezentowano również stanowisko badawcze do realizacji weryfikacji procesów skrawania pojedynczym ziarnem ściernym, które wyposażone zostało w zespół dosuwu nanometrycznego, umożliwiający realizacje dosuwu wgłębnego na poziomie atomowym
EN
This article presents the possibilities of realization of the molecular simulations in reference to processes the nano and the micropolishing of the worked surfaces. In article was presented also investigative position to realization of verification of cutting off processes with individual abrasive crystallite. This investigative position was equipped in nanometric in-feed set enabling in-feed realization on atomic level.
5
Content available remote Nanomechanical Properties of Metallic fcc Nanorods from Molecular Simulations with the Sutton-Chen Force Field
Białoskorski M., Rybicki J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2012
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Vol. 16, No 1-2
97-133
EN
Basic elastic constants (Young’s modulus, Poisson’s ratio, shear modulus) were determined for several monocrystalline, metallic (Ni, Cu, Pt, Au) nanorods using molecular dynamics with the Sutton-Chen force field. Stress-strain curves were also calculated and discussed.
6
Content available remote Mechanical Properties of Single - walled Carbon Nanotubes Simulated with AIREBO Force - Field
Białoskórski M., Rybicki J.
Computational Methods in Science and Technology
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2012
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Vol. 18, No. 2
67-77
EN
In this work we determined the mechanical properties (Young's modulus, Poisson's ratio, and shear modulus) of 400 single-walled carbon nanotubes of radii from 2.1; ((0, 5) nanotube) to 17.3 A ((0, 45) nanotube). All nanotubes were simulated with AIREBO forcefield. It turns out that zigzag nanotubes are mechanically more resistant than armchair nanotubes.
7
Content available remote Structure of Small Platinum Clusters Revised
Winczewski S., Rybicki J.
Computational Methods in Science and Technology
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2011
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Vol. 17, No. 1-2
75-85
EN
Systematic studies on the structure of platinum clusters consisting of N = 2-15 atoms were performed using density functional theory. The results show that up to N = 9 atoms planar structures are as stable as three- dimensional ones. For larger clusters, both distorted and disordered spatial structures are preferred. The global minima of N = 10- and 14-atom clusters were found to possess fcc-like structures with significantly higher stability.
8
Content available remote MD Simulations of Ultraprecision Machining of fcc Monocrystals
Rychcik-Leyk M., Białoskorski M., Dziedzic J., Rybicki J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2010
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Vol. 14, No 1-2
35-167
EN
In technical sciences, the term "machining" refers to the process of forming an object into a desired shape and size, with a desired quality of surface, by removing layers of its material by means of a cutting tool. The paper describes research on ultra-precision machining (UPM), where the abovementioned process takes place on the atomic level and involves systems (a machined object and a tool) several dozen nanometers in size. Three-dimensional computer simulations (virtual experiments) of UPM of monocrystalline copper with an infinitely hard tool were performed utilizing the classical molecular dynamics (MD) method with a many-body potential to describe the interatomic interactions. Among the examined issues were: the effect of the tool shape, machining speed and depth on the obtained workmaterial surfaces, and on the stresses, slip patterns and local temperature increases generated during the process.
9
Content available remote Model angular distribution functions in CA3, CA4 and CA6 structural units of glassy systems
Bergmański G., Feliziani S., Rybicki J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2007
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Vol. 11, No 3
185-195
EN
We have calculated model partial angular distribution functions (pADFs) in CA3, CA4 and CA6 structural units, i. e. an equilateral triangle with three vertical anions, A, and a central cation, C, a regular tetrahedron with four vertical anions, A, and a central cation, C and a square bipyramid with six vertical anions, A, and a central cation, C. The model pADFs were calculated employing a simple Monte Carlo procedure: the ions were being shifted at random within 3D spheres of radius r with uniform probability density and the AAA, ACA and CAA angles were calculated for each random configuration. Repeating the calculation 10(8) - 10(9) times produced smooth probability densities for the angles' values. Conventional reference data so obtained can be applied to estimate the overall degree of deformation of the considered structural units in numerically simulated materials.
10
Content available remote Length distribution of fuzzy-end segments
Frigio S., Cosimi G., Bergmański G., Urbańska-Galewska E., Rybicki J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2006
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Vol. 10, No 3
291-309
EN
We have calculated and discussed the probability density distributions of lengths of fuzzy-end segments, i. e. segments the ends of which assume random positions. We per-formed our calculations for several simple cases in 1, 2 and 3 dimensions: one end fixed, the other assuming a random position, and both ends at random positions. The obtained statistical data may serve as reference data for calculations of stochastic-geometrical properties of complex systems, such as conformations of complicated bolted construc-tions with clearances (in structure mechanics) or energy transfer processes between molecules in diluted systems (in physics).
11
Wielowymiarowa i wielopoziomowa przewaga konkurencyjna - aspekty teoretyczne
Nogalski B., Rybicki J.
Prace Naukowe Instytutu Organizacji i Zarządzania Politechniki Wrocławskiej. Studia i Materiały
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2005
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Vol. 76, nr 18/1
229-242
PL
Celem artykułu jest zaprezentowanie głównych kierunków we współczesnej teorii przewagi konkurencyjnej, próba uporządkowania i systematyzacji różnych podejść, jak również przedstawienie źródeł przewag konkurencyjnych na różnych poziomach strategicznych. Szczególne interesujące mogą być rozważania na temat sposobów tworzenia przewagi konkurencyjnej na następujących poziomach: otoczenia konkurencyjnego, korporacji, strategicznej jednostki biznesu i poziomie produktu. Przewag konkurencyjnych można doszukiwać się również w innych przekrojach i perspektywach, np. w jakim stopniu model biznesu może kreować różnego rodzaju przewagi konkurencyjne na poziomie produktu, czy usługi ? Autorzy artykułu pragną zasygnalizować również względność przewagi konkurencyjnej w zależności od kontekstu strategicznego. Dotyczy to głównie odpowiedzi na pytanie: dlaczego jedne przedsiębiorstwa posiadając przewagę konkurencyjną potrafią ją wykorzystać w walce konkurencyjnej na rynku a inne nie są w stanie tego dokonać? Ważnym zagadnieniem jest problem dopasowania strategicznego, czyli sformułowania odpowiedniej strategii, bazującej na osiągniętych typach przewag konkurencyjnych. Ostatnim zagadnieniem poruszonym w artykule jest problem analizy przewag konkurencyjnych w ujęciu dynamicznym, gdzie czynnik czasu jest decydujący w osiągnięciu sukcesu rynkowego a sama przewaga konkurencyjna jest rozpatrywana pod kątem labilności dystansu jaki dzieli poszczególnych konkurentów i lidera rynkowego.
EN
In our paper we tried to present briefly main directions of contemporary competitive advantage theory. We also tried to classify types of competitive advantage on various levels concentrating on nature of multilevel strategic advantage. We also focused on many forms of strategic advantage according to chosen dimensions. In our conception competitive advantage has not only multilevel nature but multidimensional as well. We have presented few matrices showing options available for companies in various market position in order to search for multidimensional competitive advantage. Our intention was to combine the core competences approach with the positioning approach to the strategic planning and multilevel analysis of chosen dimensions. The main dimensions of this concept are: willingness to learn, willingness to change, core competences, durability of competitive advantage, innovation's revolutionary aspect for market and industry. The multilevel competitive advantage can be created on following fields: network, business model, market and product. Strategic context and market strategy are two key factors which influencing the use of competitive advantage in the practice.
12
Content available remote Structure recognition in MD-simulated materials. A case study of BO3 triangles in borate glasses
Bergmański G., Białoskórski M., Rychcik-Leyk M., Rybicki J.
Materials Science Poland
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2005
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Vol. 23, No. 4
989--999
EN
In computer simulations of the structure of matter, one usually obtains the Cartesian coordinates of all the particles involved. A non-trivial problem of structure recognition and characterization arises. In the present contribution, we study in detail the geometrical properties of a fuzzy-vertex CA3 structural unit (C - cation, A - anion). Two deformation degree estimators are introduced and examined. The Monte Carlo-generated stochastic characteristics of fuzzy CA3 triangles constitute conventional reference data that can be compared with the corresponding distributions calculated for a computer-simulated material. A quantitative estimation of the deformation degree of CA3 units in the simulated structure can thus be obtained. We apply the methods developed to quantitatively characterize the geometry of BO3 structural units in B2O3 glass.
13
Content available remote The structure of rarefied and densified PbSiO3 glass: a molecular dynamics study
Bergmański G., Białoskórski M., Rychcik-Leyk M., Witkowska A., Rybicki J., Mancini G., Frigio S., Feliziani S.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2004
|
Vol. 8, No 3
393-412
EN
The paper is a molecular dynamics (MD) study of the structure of rarefied and densified lead-silicate glass of the PbSiO3 composition. Simulations have been performed in the constant volume regime for systems with densities of 3000, 4000, 5000, 5970 (normal density), 7000 and 8000kg/m3, using a two-body potential (Born-Mayer repulsive forces and Coulomb forces due to full ionic charges). All the systems were initially prepared as well equilibrated hot melts, and then slowly cooled down to 300K. The information on short-range correlations was obtained in a conventional way (from radial and angular distribution functions), while the middle-range order was studied via cation-anion ring analysis, using our new programme for basal ring determination. The structure of rarefied and densified glasses is compared with the structure of the same glasses under normal conditions. Moreover, the present results on PbSiO3 glass are compared with the corresponding data previously obtained for rarefied and densified PbGeO3 glass (Rybicki et al. 2001 Comput. Met. Sci. Technol. 7 91-112).
14
Content available remote The structure of porous and spontaneously densified amorphous PbSiO3 : a molecular dynamics study
Chomenko K., Bergmański G., Białoskórski M., Rychcik-Leyk M., Feliziani S., Frigio S., Witkowska A., Rybicki J.
Computational Methods in Science and Technology
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2004
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Vol. 10, nr 1
21-38
EN
In the paper we propose and test a "gel-drying" method of obtaining porous oxide glasses in Molecular Dynamics (MD) simulations. The simulation is started with low (screened) values of ionic charges. Then, the charges are gradually increased (to mimic the gradual elimination of a polar solvent) up to full ionic charges (a completely dry gel). This computational trick is applied to produce a porous PbSiO3 system. The structure of the resulting low-density samples is analysed in detail. Then, the porous structures are submitted to spontaneous densification, and the structure of the obtained dense bulk glasses is analysed. Finally, the structures of bulk glass obtained via spontaneous densification (density p - 8250 kg/m3) and bulk glass of the same density obtained via isotropic compression are compared.
15
Content available remote Molecular dynamics study of short and medium range order in modified BGO glasses
Walentynowicz A., Witkowska A., Białoskórski M., Rybicki J., Feliziani S., Frigio S., Cosimi G.
Computational Methods in Science and Technology
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2004
|
Vol. 10, nr 2
203-218
EN
In the paper we present our recent Molecular Dynamics (MD) simulations of the structure of bismuth-germanate (BGO) glasses of x[pBi2 (1-p)Bi2O3](1-x)GeO2 composition, where x denotes the content of the bismuth oxide in unmodified glasses, and p - the fraction of neutral bismuth that can appear in the surface modification process (e.g, annealing in hydrogen atmosphere). We consider glasses of compositions x = 0.1, 0.2, 0.3 and reduction degrees = O, 0.25, 0.5, 0.75, 1. The simulation results are analysed in detail and compared with the structural data provided by other authors.
16
Content available remote The structure of Pb-PbO-SiO2 glass via molecular dynamics simulation
Rybicki J., Witkowska A., Bergmański G., Mancini G., Feliziani S.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
|
2003
|
Vol. 7, No 2
243-256
EN
The paper is dedicated to a molecular dynamics (MD) study of the structure of partially reduced lead-silicate glass of composition 1Pb 1PbO 1SiO2. The simulations have been performed in the constant volume regime, using a two-body potential (Born-Mayer repulsive forces, and Coulomb forces due to full ionic charges). The system was initially prepared as a well equilibrated hot melt, and then slowly cooled down to 300K. The information on short-range correlations were obtained in a conventional way (from pair and angular distribution functions), while the medium-range order was studied via cation-anion ring analysis. In the paper, the short- and medium-range order in the simulated system is discussed and compared with the structure of a glassy completely reduced system, i.e. 2Pb 1SiO2 and unreduced one, i.e. 2PbO 1SiO2 glass.
17
Content available remote Gel–glass transition in silica and nitrided silica aerogels – experiment and computer modelling
Szaniawska K., Murawski L., Rybicki J., Witkowska A., Walewski M.
Optica Applicata
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2003
|
Vol. 33, nr 1
75-81
EN
Nitrided silica aerogel was sintered at 1600 °C in vacuum or nitrogen atmosphere and the effect of densification was compared with that observed in silica aerogel. It has been shown that homogeneous oxynitride glasses containing 8.4–13 wt% can be obtained by densification of nitrided aerogels. The densification process of nitrided aerogels was simulated by computer modeling using classical molecular dynamics (MD) simulations. MD simulations have shown that densification process proceeds in a similar way as in the experiment. In addition, the simulations indicate that oxynitride glasses can be obtained by densification of Si–O–N system.
18
Content available remote EXAFS study of glasses of the CaO-Ga2O3-GeO2 system
Chełstowski D., Witkowska A., Rybicki J., Padlyak B., Trapananti A., Principi E.
Optica Applicata
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2003
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Vol. 33, nr 1
125-132
EN
X-ray absorption spectroscopy (XAS) measurements for Ca3Ga2Ge3O12 and Ca3Ga2Ge4O14 glasses are presented. In particular, the extended X-ray absorption fine structure (EXAFS) spectra are analysed and local neighbourhood of Ga and Ge atoms is described in detail. The Ge/Ga atoms neighbourhood in considered glasses is compared with the data available for corresponding crystals. Performed comparative crystal-glass structural analysis confirms correlation between crystalline and glassy structures of the Ca3Ga2Ge3O12 and Ca3Ga2Ge4O14 compounds. Our results provide several new detailed data, and some general suggestions on the CaO–Ga2O3–GeO2 glass structure.
19
Content available remote A comparison between MD- and EXAFS-extracted structural data for ternary RbBrl – xIx
Bosko J., Rybicki J., Witkowska A., Principi E.
Computational Methods in Science and Technology
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2002
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Vol. 8, nr 2
7--12
EN
The structure of ternary salts of the composition RbBr1-xIx, x = 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9 and 1.0 is discussed. In particular, a comparison is made of the structural results obtained from an X-ray absorption spectroscopy (XAS) experiment and the corresponding data obtained in classical molecular dynamics (MD) simulations. In MD simulations, realized in the isobaric-isothermal (NpT) ensemble, the Dixon and Sangster's potential parameterisation (M. Dixon and M. J. L. Sangster, J. Phys. C: Solid State Phys., 9, 3381 (1976)) has been applied. The ability of the theoretical model of interatomic interaction to reproduce the structural properties observed in the EXAFS experiment is critically discussed.
20
Content available Simulation of fluid flow with interacting particles
Górecki R., Mars M., Alda W., Fioretti L., Rybicki J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2001
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Vol. 5, No 1
59-69
EN
In the paper a method for modeling flows in the presence of interacting particles is briefly presented. The method is based on merging classical, continuous approach of numerical solution of Navier-Stokes equations on the 2D mesh with discrete particles interacting with the fluid and among themselves by means of central and friction forces. Several sample simulations have been described presenting the flow through porous medium and convection flow driven by sedimentation.
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