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According to an earlier hypothesis on the relationship between the spontaneous surface segregation of a component of binary nanoparticles A–B and the stability/instability of nanostructures of the core-shell type (A@B and B@A, where the first component corresponds to the core of a particle and the second to its shell), the stability should be the same as that of the nanostructure whose shell corresponds to the component of binary nanoparticles spontaneously segregating to the surface. This hypothesis is tested, and possible deviations from this pattern are identified through the atomistic modeling of Co@Au, Au@Co, Ni@Cu, and Cu@Ni nanostructures.

Employing classical isothermal molecular dynamics, we simulated coalescence of mesoscopic Au nanodroplets, containing from several thousands to several hundred thousands of atoms, and sintering of mesoscopic solid Au nanoparticles. For our atomistic simulations, we used the embedded atom method. The employed open access program large-scale atomic/molecular massively parallel simulator makes it possible to realize parallel graphical processing unit calculations. We have made a conclusion that the regularities and mechanisms of the nanodroplet coalescence (temperature is higher than the nanoparticle melting temperature) and of the solid nanoparticle sintering differ from each other. We have also concluded that the nanodroplet coalescence may be interpreted as a hydrodynamic phenomenon at the nanoscale whereas sintering of solid nanoparticles is a much more complex phenomenon related to different mechanisms, including collective rearrangements of atoms, the surface diffusion, and other types of diffusion. At the same time, collective rearrangements of atoms relate not only to the solid nanoparticle sintering but also to the nanodroplet coalescence. In general, our molecular dynamics results on sintering of Au nanoparticles consisting of 10 000–30 000 atoms agree with the Ferrando–Minnai kinetic trapping concept that was earlier confirmed in molecular dynamics experiments on Au nanoclusters consisting of about 100 atoms.

Investigation of properties of nuclear matter at extremely high temperature and/or extremely high baryon densities under laboratory conditions is one of the fundamental lines of research in high-energy physics. Throughout the past decades, such investigations have been performed in collisions of ultrarelativistic heavy ions in several experiments at modern accelerator complexes, including the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL, USA) and the Large Hadron Collider (LHC) at CERN (Switzerland). In the near future, it is also planned to launch investigations of this kind at the FAIR (Facility for Antiproton and Ion Research at Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany) and NICA (Nuclotron-based Ion Collider fAcility at Joint Institute for Nuclear Research (JINR), Dubna, Russia) accelerators. In order to implement such investigations, it is necessary to create sophisticated detector systems that are able to record events featuring high-multiplicity product particles and to measure reliably their properties. The present article gives a brief survey of all detector systems that have already been created and are being developed at Laboratory of Relativistic Nuclear Physics at Petersburg Nuclear Physics Institute (National Research Center Kurchatov Institute) for the PHENIX (BNL, USA), ALICE (CERN, Switzerland), and CBM (GSI, Germany) experiments aimed at studying nuclear matter under extreme conditions.

Regularities and mechanisms of coalescence of Au nanodroplets and sintering of solid Au nanoparticles have been investigated by using molecular dynamics and some theoretical models. It has been established that the characteristic time of coalescence t is proportional to radius r0 of initial nanodroplets. Both the above conclusion and some quantitative estimations of the proportionality coefficient between t and r0 agree with Frenkels theory (1946) though this theory was rut forward to describe coalescence of macroscopic droplets.

Two alternative molecular dynamics models (programs) involving the Gupta (tight-binding) potential have been used to reproduce the dealloying phenomenon in the Au – Ag nanoalloy. Program I successively removes Ag atoms from the particle surface layer (we simulated nanoparticles consisting initially of 1500 Au and 1500 Ag atoms). Program II proposes search and removing atoms with lowest specific binding energies. We have found that as a result of dealloying the particle surface layer is really enriched with Au atoms. However the particle core keeps in general the structure of the initial nanoalloy. We have also established that dealloying results in formation a defected particle structure (vacancies, first of all). Presumably, just such an effect yields the porous structure of bigger Au – Ag particles in laboratory experiments on dealloying.

In this work, we performed atomistic modeling of the behavior of Co (core) – Au (shell) and Au (core) – Co (shell) during thermal exposure in order to study the stability/instability problem for the above nanostructures using the tight binding potential and two alternative computer programs based on the molecular dynamics and Monte Carlo methods. It has been shown that both the Co (core) – Au (shell) and Au (core) – Co (shell) structures can be stable. However, molecular dynamics results predict a short-term decay of Au2500 (core) / Co2500 (shell) nanostructures in a high-temperature region followed by a self-assembly, while the Monte Carlo method predicts the appearance of defects – cavities in the particle core and on the boundary between two components. It is concluded that the size effect can be the main factor determining stability/instability for the Co (core) – Au (shell) and Au (core) – Co (shell) structures.

Phase-change memory is based on a change in the optical, electrical, or other properties of a substance during a phase transition, for example, transition from the amorphous to the crystalline state. Already realized and potential applications of such memory are associated with the use for this purpose of multicomponent alloys based on metals, semiconductors. However, single-component nanoparticles, including Si ones, are also of interest in view of the prospects for their use as nanoscale memory units. In particular, possibility of creating such memory units is confirmed by the fact that the bulk phase of the amorphous silicon has an optical absorption coefficient which is by an order of magnitude greater than that of the crystalline, although, it is difficult to release this effect for an individual nanoparticle whose size does not exceed the wavelength of light. In this work, using molecular dynamics (MD) and the Stillinger-Weber potential, we studied the laws of melting and conditions of crystallization for silicon nanoparticles containing up to 100,000 atoms. It has been shown that upon cooling a silicon nanodroplet at a rate of 0.2 TK/s and higher rates, its transition into the amorphous state takes place, whereas single-component metal nanodroplets crystallize even at cooling rates of 1 TK/s. Upon subsequent heating of amorphous silicon nanoparticles containing more than 50,000 atoms, they crystallize in the definite temperature range 1300—1400 K. It is concluded that it is principally possible to create memory units based on the above phase transitions. The transition of a nanoparticle to the amorphous state is achieved by its melting and subsequent cooling to the room temperature at a rate of 0.2 TK/s, and switching to the crystalline state is achieved by heating it to 1300—1400 K at a rate of 0.2 TK/s and subsequent cooling. On the basis of results of MD experiments, a conclusion is made that there exist a minimal size of silicon nanoparticles, for which producing memory units based on the change of the phase state, is not possible. It was found that for the temperature change rate of 0.2 TK/s, the minimal size in question 12.4 nm that corresponds to 50,000 atoms.

Phase diagrams for Au-Si nanoparticles were constructed by using molecular dynamics and thermodynamic simulation, based on the CALPHAD methodology extended to nanoscale objects. It was established that the eutectic temperature of nanoparticles decreases by about 200 K compared to the bulk eutectic temperature, and the position of the eutectic point slightly shifts to a lower value of the molar fraction of Si.

The size dependences of the temperatures of melting $${{T}_{{\text{m}}}}$$ and crystallization $${{T}_{{\text{c}}}}$$ of Co nanoparticles and also those of the heat (enthalpy) of melting $$\Delta {{H}_{{\text{m}}}}$$ and crystallization $$\Delta {{H}_{{\text{c}}}}$$ are studied using a complex approach to atomistic simulation combining the use of the molecular dynamic and Monte Carlo methods. It is established that $${{T}_{{\text{m}}}}$$ and $${{T}_{{\text{c}}}}$$ decrease linearly with increasing inverse particle radius. The phase transition heats $$\Delta {{H}_{{\text{m}}}}$$ and $$\Delta {{H}_{{\text{c}}}}$$ also decrease during the transition from the bulk phase to nanoparticles, but it seems this effect is non-scalable.

Surface segregation in Ni–Cu binary nanowire is studied using an integrated approach that combines atomistic (molecular dynamics) and thermodynamic simulation. It is shown that a tendency toward the spontaneous surface segregation of Cu atoms is a factor that stabilizes bimetallic structure Ni (core)/Cu (shell) and destabilizes structure Cu (core)/Ni (shell).

The regularities and mechanisms of coalescence of Au nanodroplets and sintering of solid Au nanoparticles are investigated using molecular dynamics experiments and some theoretical models. It is established that the characteristic time of coalescence τ is proportional to the radius r0 of the original nanodroplets. Both the conclusion and the quantitative estimations of the proportionality coefficient between τ and r0 agree with Frenkel’s theory (1946), yet this theory was proposed for describing the coalescence of macroscopic droplets.

The size dependence of the melting point of Si nanoparticles is investigated using molecular dynamics and thermodynamic simulation based on the Thomson’s formula. The atomistic modeling data obtained using the Stillinger–Weber potential agree with the results reported by other authors and thermodynamic-simulation data and predict a decrease in the melting point Tm of Si nanoparticles with an increase in their reciprocal radius R–1 according to linear law. The available experimental data predict lower Tm values, including the limiting value $$T_{m}^{{(\infty )}}$$ , which corresponds to the linear extrapolation of experimental points to R–1 → 0 (to the radius R → ∞); the underestimation is 200–300 K as compared with the reference melting point of silicon (1688 K). It is concluded that the molecular-dynamics data on Tm(R–1) obtained using the Stillinger–Weber potential are more adequate than the available experimental data.

The linear relationship between surface tension γs and radius $$~{{R}_{{\text{s}}}}$$ of small particles (nanoparticles) was derived in the 1960s by Rusanov as $${{{\gamma }}_{{\text{s}}}} = K{{R}_{{\text{s}}}},$$ where K is the coefficient of proportionality. In this work, a more generalized dependence is obtained in the context of Gibbs’ theory of thermodynamics for curved interfaces on the same size scales for a randomly selected interface, including an equimolecular surface with radius $${{R}_{{\text{e}}}}{\text{.}}$$ It is shown that when $${{R}_{0}} \geqslant R \geqslant {\delta }$$ (where $${\delta } = {{R}_{{\text{e}}}} - {{R}_{{\text{s}}}},$$ $${{R}_{0}}$$ is a characteristic radius limiting the range of the Rusanov equation’s applicability), linear dependence $${\gamma } = KR$$ should be valid for all $$R \in \left[ {{{R}_{{\text{s}}}},{{R}_{{\text{e}}}}} \right].$$ Parameter $$K~$$ is estimated for metal nanodroplets and solid metal nanoparticles as well.

The phenomenon of solid state wetting is studied via molecular dynamics (MD) in a Pb (nanoparticle)/Cu (substrate) system. It is found to be associated with capillarity-induced surface diffusion (CISD). This conclusion is confirmed by the coincidence between the MD-estimated characteristic nanoparticle spreading time and the evaluations made in the context of CISD.

A molecular dynamics method developed on the basis of the classical nucleation theory for calculating the interfacial energy at melt–crystal interfaces has been extended to binary metal systems. The temperature dependence plotted for the interfacial energy of a Pb–Cu bimetallic system within a range of 1025–1125 K is in good agreement with the results of the statistical calculations performed within the framework of a simplified quasi-crystalline coherent model of the liquid phase and the interface taking into account the interatomic interactions with the closest neighbors. A similar methodology may be used to determine the interfacial energy for a wide spectrum of multicomponent metal systems, if the interparticle interaction potentials have been reliably determined for them.

Size dependence of the melting temperature of Si nanoparticles has been investigated combining molecular dynamics and thermodynamic simulations. The results of the atomistic simulation obtained using the Stillinger-Weber potential agree with the results of other authors and with the thermodynamic simulation results based on Thomson’s formula. These results predict that the melting temperature Tm of Si nanoparticles diminishes with increasing their reciprocal radius R-1 following to the linear law. The available experimental data predict much lower values of Tm, including underestimated values of the limiting value Tm(∞) found by means of the linear extrapolation of experimental dots to R-1 → 0 (i.e. to the particle radius R → ∞), and the underestimation of Tm(∞) ranges from 200 to 300 K in comparison with the melting point 1688 K of the bulk crystalline Si. Taking into account the obtained results and their comparison with available results of other authors, a conclusion is made that molecular dynamics results, obtained by using the Stillinger-Weber potential, should be more adequate than the available experimental data on the melting temperature of Si nanoparticles.

Using available experimental data on evaporation rates for metal nanoparticles and shrinkage rates for vacancy pores, evaluations have been performed of the particle size ranges where the linear dependence σ = Kr between the surface tension σ and the particle radius r. The reliability intervals have been found for the proportionality coefficient K. The results obtained are compared to evaluations by E.N. Vitol (1992). On the bases of the results of these evaluations a conclusion has been confirmed that a thermodynamic stability condition obtained before is fulfilled for nanoparticles of all metals considered in the paper.

The size dependences of the melting and crystallization temperatures of silver nanoparticles are obtained by two alternative atomistic simulation methods, such as the molecular dynamics and Monte-Carlo methods. The simulation results are analyzed and compared with available experimental values and a melting temperature calculated using the well-known Thomson formula. Atomistic simulation reveals good coincidence between the data and satisfactorily conforms to the Thomson formula. However, the melting temperatures predicted through atomistic simulations exceeds the available experimental data.

Size dependences of the melting temperature Tm and binding energy E, i.e., their dependences on the particle radius R, have been investigated by employing thermodynamics, a local coordination approximation for E as well as molecular dynamics. We have found that both quantities Tm and E decrease at decreasing the particle size and follow to the linear or close to linear dependence on the reciprocal particle radius R−1. However, Tm(R−1) and E(R−1) dependences are characterized by different values of the slope coefficients : KT > 1 whereas KE Rch) to region II of metal nanoclusters (R

An approach combining thermodynamic and atomistic (molecular dynamics) simulations has been applied to predict surface segregation in binary metal A–B nanoparticles (Cu–Ni and Au–Co ones). The thermodynamic simulation method based on the Butler equation was additionally justified and extended to stationary non-equilibrium states using the energetic variant of non-equilibrium thermodynamics. The results of thermodynamic and atomistic simulations agree with each other predicting segregation of Cu atoms to the surface of Cu–Ni nanoparticles and the surface segregation of Au in binary Au–Co nanoparticles. A hypothesis is put forward on correlation between stability/instability of A (core)/B (shell) nanostructures and the spontaneous surface segregation of one of the components of binary A–B nanoparticles. In accordance with this hypothesis, the core–shell structure A (core)/B (shell) will be stable if the component B spontaneously segregates to the surface of binary A–B nanoparticles. At the same time, a trend to the surface segregation of this component should result in the instability of the B (core)/A (shell) structures. The hypothesis in question agrees with our molecular dynamics results and with available experimental data on stability/instability of Co (core)/Au (shell) and Au (core)/Co (shell) nanostructures.

Size dependences of melting and crystallisation entropies of metal nanoparticles (of copper and gold) have been studied using atomistic simulation results (molecular dynamics and Monte Carlo) and some theoretical considerations. The size dependence of melting entropy is more pronounced than that of crystallisation entropy. The behaviour of the size dependence of the melting entropy has been found to be complex and ambiguous. However, all thermodynamic models predict that the melting entropy of nanoparticles is lower than the corresponding bulk value and increases with growing particle size, and tends to the bulk value when the particle size tends to infinity.

Equilibrium contact angles are measured for molten germanium droplets on surfaces of fused quartz and other materials pretreated using different options of grinding, polishing, and (in some cases) etching. The roughness factors of relief profiles are estimated via optical interferometry. It is found that depending on the means of treatment, the contact angle varies within a fairly wide range: from 147° to 164°. Based on the final results, it is concluded that the Wenzel–Derjaguin equation is not applicable to the considered system.

Equilibrium contact angles of melted geranium have been measured at fused quartz surfaces. The surfaces were preliminarily grinded, polished, and, in some cases, etched. Then, the roughness coefficients are determined for the relief profile and the surface itself by optical interferometry using a NanoMap 1000 WLI profilometer. The contact angle has been found to vary in a range of 147°–164° depending on the method of surface pretreatment. The measured values of the contact angles agree with the data of other researchers. At the same time, the analysis of the obtained data has led to the conclusion that Wenzel’s equation, which relates the contact angles at smooth and rough surfaces, is not valid for germanium droplets on quartz surface.

An approach combining atomistic molecular dynamics (MD) and thermodynamic simulations has been applied to predict the distribution of components in binary Ni–Cu and Au–Ag nanoparticles consisting of 2000 atoms (of about 4 nm in size). The term ‘thermodynamic simulation’ has referred to solving, in some approximations, the Butler equation for a core–shell particle model. Both atomistic and thermodynamic approaches predict the surface segregation of Cu atoms in Ni–Cu nanoparticles and segregation of Ag to the surface of Au–Ag nanoalloys. Then, contrary to the Ni–Cu systems, some Au–Ag nanoparticles demonstrated an onion-like structure with the outer Ag monolayer. The results of MD and thermodynamic simulations agree with each other and with some available direct and indirect experimental data.

Using the isothermal molecular dynamics and the tight-binding potential, crystallization of Ti6Al4V nanodroplets was simulated. The objects of the research consisted of 2869 atoms, including 172 Al atoms and 115 V ones. The OVITO program was employed to recognize local structures and nanophases arisen in the course of cooling nanoalloy with the cooling rates of 0.1 and 0.4 K/ps. We have found that the cooling rate effect on the structure of the Ti6Al4V nanoalloy and the thermally induced structural transformations is much more pronounced than the size effect.

Earlier we put forward a hypothesis about relationship between the spontaneous surface segregation of one of the components of binary A-B nanoparticles and stability/instability of one of the two alternative core-shell nanostructures A@B or B@A. Here, the first symbol (before the @ sign) corresponds to the particle core, and the second (after @) to its shell. In accordance with our hypothesis, stable or at least more stable should be that of the two alternative nanostructures, the shell of which corresponds to the component spontaneously segregating to the surface. Verification of this hypothesis and revealing possible deviations from it have been carried out by using molecular dynamics simulation of Co@Au, Au@Co, Ni@Cu, Cu@Ni, Al@Ni and Ni@Al nanostructures. In addition, the atomistic and thermodynamic simulations were involved to predict the surface segregation in corresponding binary nanoalloys (Co-Au, Ni-Cu and Ni-Al). The thermodynamic simulation of segregation in binary metal nanoparticles was based on numerical solution of the Butler equation for a two-cell particle model. It has been established that the above hypothesis is indeed fulfilled but in some certain temperature ranges. During discussion of the results obtained, the concept was put forward of thermodynamic and kinetic factors of the core-shell nanostructure stability.

Isothermal molecular dynamics is used to find the magic numbers corresponding to clusters of fcc transition metals: silver and copper. To that end, we use both our own computer program with a tight-binding potential and well-known LAMMPS software whose standard package is designed to model metal systems by the embedded atom method. Regardless of the choice between two relaxation techniques (lowtemperature relaxation at 1 K and the variant involving a gradual temperature decrease with subsequent relaxation at 1 K), magic number 13 is detected that corresponds to the first term of the Chini series. At the same time, other magic numbers are also found that belong and do not belong to this series.

Confidence intervals for proportionality coefficient K in Rusanov’s linear dependence σ = Kr between surface tension σ and particle radius r are estimated for the first time using experimental data on the rates of small metal particle evaporation and vacancy pore shrinkage. The results are compared to earlier estimates by E.N. Vitol (1992) and thermodynamic estimates of other authors.

It is proposed that the dimension of similarity of the relief profile be used as an integral characteristic of solid-surface roughness. This parameter coincides with the fractal dimension of the line only in the case of the same length scales in the surface plane and in the direction that is normal to it. The interrelation between the dimension of similarity and the usually used fractal dimension of the relief profile is obtained and analyzed. The optical surface of single-crystal Ge is used as an example in order to reveal the correlation between the dimension of similarity of the relief surface and the transmission coefficient in the infrared range.

Aim. To study the processes of free-radical oxidation, antioxidant defense, energy metabolism, electrolyte metabolism, and cytokine system reflecting the state of the non-specific defense of the body in workers exposed to complex of toxic substances under the conditions of manufacturing, substantiating the importance of indicators of preclinical diagnosis of disease development risk.Methods. The study included 90 workers of JSC «Experimental Plant Neftekhim», 95 workers of JSC «Kaustic» and 101 workers of JSC «Ufa plant of elastomeric materials, products and structures». Materials for the study were blood, mixed saliva, gingival fluid and urine. The laboratory studies were performed to evaluate the free radical oxidation processes, antioxidant defense, energy metabolism, electrolyte metabolism, and cytokine system. Taking into account the features of industrial factors, particularly their effects on the workers bodies, routes of toxic compounds entry by inhalation, oral cavity and skin of the hands, three professional groups were formed (A, B, C). Group A included employees having constant contact with chlororganic compounds. The group B included persons who have constant contact with the higher and lower aromatic hydrocarbons. A group C consisted of employees who have constant contact with a mixture of chemicals: rubber compound containing carcinogens - benzo(a)pyrene, NDMA, nitrosodiethylamine; white carbon black, rubber dust, talc, amine compounds, sulfur dioxide, carbon monoxide. The control group consisted of employees of administrative and managerial staff.Results. The study revealed that one of the major pathogenetic mechanisms of action of chemical and petrochemical industry hazards is activation of free radical oxidation.Conclusion. Among the mechanisms of the influence of chemical contaminants of working environment a leading role play intensification of free radical oxidation processes, failure and/or inhibition of the antioxidant defense components.

The spreading of solid Cu nanoparticles (1–10 nm in diameter) on the (100) Cu surface and solid Au nanoparticles on the (100) Au face is simulated via molecular dynamics. The results for the Cu (nanoparticle)/( 100) Cu system are compared with the available experimental data for Cu microparticles (0.1–10 μm) spreading on the polycrystalline Cu surface. The solid-state spreading phenomenon is found to play an important role in many natural and technological processes. Some potential applications in nanotechnology and restrictions in the operation characteristics of nanosized units and nanomaterials are discussed as well.

The generalized Thomson formula Tm = Tm(∞)(1-δ)R for the melting point of small objects Tm has been analyzed from the viewpoint of the thermodynamic theory of similarity, where R is the radius of the particle and Tm(∞) is the melting point of the corresponding large crystal. According to this formula, the parameter δ corresponds to the value of the radius of the Tm(R-1) particle obtained by the linear extrapolation of the dependence to the melting point of the particle equal to 0 K. It has been shown that δ = αδ0, where α is the factor of the asphericity of the particle (shape factor). In turn, the redefined characteristic length δ0 is expressed through the interphase tension σsl at the boundary of the crystal with its own melt, the specific volume of the solid phase vs and the macroscopic value of the heat of fusion λ∞:δ0 = 2σslvs/λ∞. If we go from the reduced radius of the particle R/δ to the redefined reduced radius R/r1 or R/d, where r1 is the radius of the first coordination shell and d ≈r1 is the effective atomic diameter, then the simplex δ/r1 or δ/d will play the role of the characteristic criterion of thermodynamic similarity. At a given value of α, this role will be played by the simplex Estimates of the parameters δ0 and δ0/d have been carried out for ten metals with different lattice types. It has been shown that the values of the characteristic length δ0 are close to 1 nm and that the simplex δ0/d is close to unity. In turn, the calculated values of the parameter δ agree on the order of magnitude with existing experimental data.

The specific surface energy of small nanoclusters of transition fcc metals is calculated using the many-particle tight-binding potential and its earlier analog, the Gupta potential. The calculations are performed using both a theoretical model and computer simulations based on the Monte Carlo method. The equimolecular surface is considered as the dividing surface. It is found that at short radii of the nanoclusters, the surface energy and surface tension grow linearly as the particle radius increases. The values of the coefficient of proportionality in the dependence of the specific surface energy on the radius of a nanocluster are compared to the available literature data, experimental and otherwise.

The effect of heating and cooling rates on melting (Tm) and crystallization (Tc) temperatures of metal nanoclusters is investigated in terms of the isothermal molecular dynamics. We report on the results obtained for nickel nanoclusters, although analogous results were also obtained for gold and aluminum nanoclusters. It is found that Tm increases, while Tc decreases with increasing heating and cooling rates, both Tm and Tc tending to the same value for heating and cooling rates tending to zero. The results indicate that the hysteresis of melting and crystallization of nanoparticles must be completely due to nonequilibrium conditions of heating and cooling. The transition of Ni nanoclusters to the amorphous state begins at very high cooling rates exceeding 10 TK/s.

The many-particle tight-binding potential has been employed to calculate the specific surface energy of icosahedral nanoclusters of transition metals. The equimolecular surface has been considered as the dividing surface. The surface energy has been shown to linearly increase with particle size at nanocluster radii smaller than five radii of the first coordination sphere. As the nanocluster radius is further enlarged, the surface energy passes through a maximum and approaches an asymptotic macroscopic value. The coefficients of proportionality between the specific surface energy and nanocluster radius have been found and compared with the data available from the literature.

AFM images are used to determine and analyze fractal characteristics (cluster fraction dimension and lacunarity) of aggregates of Au and Ag nanoclusters on metal films of the same metal produced with the aid of thermal vacuum deposition on mica surface. A fractal dimension of 1.6 that corresponds to typical samples with relatively uniform distribution of nanoclusters on the film surface is in agreement with the mean value calculated from experimental data of Belko et al., who studied the fractal dimension of Au nanoclusters on a different dielectric (quartz) surface. When a compact single aggregate of Au nanoclusters is formed on a certain active center or defect, the fractal cluster dimension decreases to 1.4. The experimental data are compared with the results of existing theoretical models of association of nanoclusters in 2D systems.

Isosteric heats of hydrogen, nitrogen, and methane adsorption on graphite surface have been calculated and analyzed using the density functional theory. The heats of adsorption have been calculated within wide ranges of pressures and subcritical temperatures. The peaks in the temperature dependences of isosteric heat of adsorption have been found to correlate with the degrees of filling of monolayers during adsorption.

Performance of the gas-filled detector prototypes based on the GEM, TGEM, and Micromegas technologies was studied on the test beam of the CERN PS accelerator. Three-component mixtures based on Ar and He were used as the working gas. For all tested detector prototypes, the gas amplification factors were measured, and the detection efficiencies, cluster distributions, and the radii of the charge cloud collected on the readout electrode were estimated.

Performance of the gas-filled detector prototypes based on the GEM, TGEM, and Micromegas technologies was studied with the aim of selecting variants for tracking detectors of the muon system for the CBM Experiment. The study was performed on the test beam of the proton accelerator at the Petersburg Nuclear Physics Institute (PNPI). Three-component mixtures based on Ar and He were used as the working gas. For all tested detector prototypes, the detection efficiencies were measured, and the modification of the amplitude spectra as a function of the incident beam intensity was investigated.

An asymmetric system of colliding copper and gold nuclei (Cu + Au) has a specific overlap geometry when compared to symmetric systems (Au + Au, Cu + Cu). Studying asymmetric heavy systems allows us to obtain additional restrictions for existing models and more accurate descriptions of the processes of parton energy loss in hot and dense QCD matter produced in collisions of heavy nuclei. This work reports nuclear modification factors for neutral pions in Cu + Au, Сu + Cu, and Au + Au collisions at an energy of 200 GeV, measured in the PHENIX experiment on the RHIC.

Two basic alternative atomistic simulation methods (molecular dynamics and Monte-Carlo) have been used to reproduce the dealloying phenomenon in Cu-Pt nanoalloys. Using the Gupta (tight-binding) potential, we simulated nanoparticles consisting initially of 1500 Cu and 1500 Pt atoms. The involved programs propose search and following removing Cu atoms with the lowest specific binding energies. We have found that as a result of dealloying the particle surface layer is really enriched with Pt atoms. However the particle core keeps in general the structure of the initial nanoalloy. This effect is especially noticeable in molecular dynamics simulation. We have also established that dealloying results in formation of a defected particle structure (vacancies, first of all). Presumably, just such an effect yields the porous structure of bigger Cu-Pt particles in laboratory experiments on dealloying.

Phase diagrams for Au-Si nanosystems were calculated by using thermodynamic simulation (NANOCALPHAD methodology) and molecular dynamics (MD). Thermodynamic simulations have been carried out for two Au-Si nanosystems: (i) a solid (crystalline) Si or Au nanoparticle (NP) contacting with an Au-Si nanodroplet of the same radius; (ii) a cylindrical Si nanowire (nanowhisker) with an Au-Si nanodroplet on its butt. We have found that the eutectic temperature of the first system decreases in comparison with the bulk eutectic temperature, and the position of the eutectic point slightly shifts to a lower value of the molar fraction of Si that agree with MD results obtained on another system, i.e. on spherical Au-Si NPs. Contrary to the first system, the eutectic temperature of the second one, i.e. of the system “Si nanowhisker -- Au-Si nanodroplet” increases in comparison with the bulk phase diagram. An explanation of such a result is proposed and discussed.

Fluctuations of energy egr; E in the canonical ensemble and of temperature egr; T in the micro-canonical one have been evaluated theoretically as well as employing the isothermal and adiabatic molecular dynamics (MD), respectively. MD experiments were performed on Au NPs in the size range from 1.0 to 15.0 nm. As secondary results, MD data on the temperature dependence of the heat capacity of Au NPs are also obtained and analyzed. Theoretical evaluations of egr; E and egr; T satisfactory or, in some cases, very well agree with our MD results on Au NPs. We have found that egr; T is by about two orders of magnitude higher than egr; E . However, even for very small NPs (nanoclusters) consisting of 55 atoms egr; T is of order of 10 % only. So, a conclusion is made on applicability of both the Gibbs ensemble method and the notion of temperature in its conventional sense to NPs.

A method for determining the proportionality coefficient K in the Rusanov linear formula σ = KR for the surface tension σ of a small object using the size dependence e(R) of the specific total surface energy (R is the particle radius) is proposed. Unlike the function σ(R), the dependence e(R) is easily found as a result of the computer simulation of nanoparticles.

Collisions between asymmetric nuclei (Cu–Au) differ significantly in their nuclear overlap geometry from those of symmetric nuclei (Cu–Cu, Au–Au). This results in a number of consequences that allow us to obtain more comprehensive and accurate information about the fundamental properties of matter under extreme conditions. The High Energy Proton–Proton Collider Experiment (PHENIX) at the Relativistic Heavy Ion Collider (RHIC) measured the nuclear modification factors of π-mesons in Cu+Au collisions at an energy of 200 GeV. New experimental data from measurements of light hadron flows of different orders (ν1, ν2) in Cu + Au collisions at an energy of 200 GeV are discussed.

The size dependence of the melting temperature T m of nanoscale metal (Sn, Cu) films on solid substrates made of another high-melting metal and carbon is studied. It is established that an increase in the melting temperature must be observed for metal films on C substrates as the film thicknesses decrease. For a system consisting of a metal film on the surface of another metal, the dependence of the melting temperature on the film thickness is less pronounced and corresponds to a decrease in T m with decreasing h (h is the film thickness).