Influence of migration the radiation-induced excitations in hetero-fullerenes C58Si2 and C68Si2 of their probability of damage

Theoretically investigated the role of migration of radiation-induced excitation in the damaged hetero-fullerenes C58Si2 and C68Si2. Defined expressions for the probability collapse of fullerenes different structures. Investigate the changing probability on irradiated conditions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2091

Formation of Chemical Compound Layer at the Interface of Initial Substances A and B with Dominance of Diffusion of the A Atoms

A theoretical approach to consider formation of chemical compound layer at the interface between initial substances A and B due to the interfacial interaction and diffusion is developed. It is considered situation when speed of interfacial interaction is large enough and diffusion of A-atoms through AB-layer is much more then diffusion of B-atoms. Atoms from A-layer diffuse toward B-atoms and form AB-atoms on the surface of B-layer. B-atoms are assumed to be immobile. The growth kinetics of the AB-layer is described by two differential equations with non-linear coupling, producing a good fit to the experimental data. It is shown that growth of the thickness of the AB-layer determines by dependence of chemical reaction rate on reactants concentration. In special case the thickness of the AB-layer can grow linearly or parabolically depending on that which of processes (interaction or the diffusion) controls the growth. The thickness of AB-layer as function of time is obtained. The moment of time (transition point) at which the linear growth are changed by parabolic is found

Critical Exponents in Percolation Model of Track Region

Numerous experiments on defect formation in insulators, metals, alloys, and amorphous semiconductors have shown that these materials are sensitive to track formation when they are bombarded by swift heavy ions (SHI). Detail understanding of the basic processes of materials modification by SHI will help to construct materials with preassigned properties. Tracks were examined like a chain of deal spherical regions; it was assumed that each incident ion creates one such chain. In this model, we assume that the track is formed randomly, but in that place of the ion path, where the energy value, which loses each ion to the unity of the way, is above some threshold value. As a result of irradiation the number of tracks will continue to grow, areas of the single tracks modified substance continue to overlap, form of modified matter becomes more complicated, creating branched structure. Based on the scaling hypothesis large-scale curve were constructed, critical exponents for this percolation model was established. Two such curves were evaluated: in the case of non-equiprobable distribution of tracks regions in depth with ratio of critical exponents ( / )s 0.68 and in the case with equiprobable distribution of tracks regions in depth, so-called model of continuous percolation with ratio of critical exponents ( / )e 0.41. Differences between critical exponents of this model and the continuous percolation model indicate that the dependence of the modified structure area on the dose and the angle related with the correlation between individual tracks. It results in next effect: angular dependence of the surface area of the branched structure has maximum value at certain «critical» angle of ions incidence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2491

Critical exponents in percolation model of track regions with different depth distribution

As a result of irradiation with Xe with E = 250 MeV in InP at room temperature [1] defects, similar to the "chain of pearls”, which are placed along the trajectory of the ions at depths ranging from 35 to 100 nm and from 7 to 10 microns have been identified. Such defects called tracks, and they can occur at different depths and have different shapes. Tracks were examined like a chain of deal spherical regions; it was assumed that each incident ion creates one such chain. In this model, we assume that the track is formed randomly, but in that place of the ion path, where the energy value, which loses each ion to the unity of the way, is above some threshold value. As a result of irradiation the number of tracks will continue to grow, areas of the single tracks modified substance continue to overlap, form of modificated matter becomes more complicated, creating branched structure. Percolation threshold, fraction of spanning cluster modified material for different doses and different distributions of track areas in depth were evaluated. Based on the scaling hypothesis large-scale curve were constructed, critical exponents for this percolation model were established. Calculated values of critical exponents were compared with the known values for the model of continuous percolation. Parameters of the percolation and critical exponents depend on the distribution of track areas in depth, which indicates the difference in the order parameters of the track structure obtained for different distributions in depth. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2081

Influence of Fluctuations of the Point-Defects’ Generation Rate and Inhomogeneity of Irradiated F.C.C. Crystal on the Temperature Dependence of the Dissipative-Structure Period in a Spatial Distribution of Radiation Vacancies

A kinetic model for the influence of external noise, such as fluctuations of the point-defects’ production rate and inhomogeneity of irradiated f.c.c. crystal, on the formation of modulated defect-distribution structure is considered. Defect-production rate and density of sinks for point defects are simulated as independent uniform and stationary stochastic fields with certain parameters. The interaction between vacancies is taken into account. Such stochastic fields can induce a spatial point-defects’ distribution, which is a stationary uniform stochastic field. Its mean value and correlation functions are estimated, and restricting conditions are determined when this stochastic field becomes unstable because of interaction between defect- density fluctuations and a stochastic field with a spatially-periodic mean value is formed. A formula for evaluating its spatial period is analysed. This geometrical parameter of such a dissipative structure is determined also by kinetic characteristics. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3543

Features of the transient creep under an irradiation

В работе теоретически получена временная зависимость скорости ползу- чести металла под облучением. Установлены условия существования рав- ных нулю минимумов скорости ползучести и времена их появления. Ис- следовано, как меняется положение провалов скорости ползучести с из- менением температуры облучения. Полученные результаты сопоставлены с экспериментально наблюдаемыми зависимостями скорости ползучести от времени.В роботі теоретично одержано часову залежність швидкости плазучости металу під опроміненням. Встановлено умови існування рівних нулю мі- німумів швидкости плазучости та часи їх появи. Досліджено, як зміню- ється положення провалів швидкости плазучости зі зміною температури опромінення. Одержані результати порівняно з експериментально спо-стережуваними залежностями швидкости плазучости від часу.The temporal dependence of creep rate of metal under an irradiation is theoretically obtained in this paper. The conditions of zero minimums of the creep-rate existence as well as the times of their appearance are determined. The changing of the position of creep-rate dips in the conditions of the temperature exposure change is investigated. The obtained results are compared with the experimentally observed dependence of the creep rate on time.http://mfint.imp.kiev.ua/en/index.htmlam2017Physic

The influence of radiation-induced vacancy on the formation of thin-film of compound layer during a reactive diffusion process

A theoretical approach is developed that describes the formation of a thin-film of AB-compound layer under the influence of radiation-induced vacancy. The AB-compound layer is formed as a result of a chemical reaction between the atomic species of A and B immiscible layers. The two layers are irradiated with a beam of energetic particles and this process leads to several vacant lattice sites creation in both layers due to the displacement of lattice atoms by irradiating particles. Aand B-atoms diffuse via these lattice sites by means of a vacancy mechanism in considerable amount to reaction interfaces A/AB and AB/B. The reaction interfaces increase in thickness as a result of chemical transformation between the diffusing species and surface atoms (near both layers). The compound layer formation occurs in two stages. The first stage begins as an interfacial reaction controlled process, and the second as a diffusion controlled process. The critical thickness and time are determined at a transition point between the two stages. The influence of radiation-induced vacancy on layer thickness, speed of growth, and reaction rate is investigated under irradiation within the framework of the model presented here. The result obtained shows that the layer thickness, speed of growth, and reaction rate increase strongly as the defect generation rate rises in the irradiated layers. It also shows the feasibility of producing a compound layer (especially in near-noble metal silicide considered in this study) at a temperature below their normal formation temperature under the influence of radiation.National Research Foundation (NRF) of South Africa.http://www.elsevier.com/locate/jpcs2017-05-31hb201

Critical exponents in percolation model of track region

Numerous experiments on defect formation in insulators, metals, alloys, and amorphous semiconductors have shown that these materials are sensitive to track formation when they are bombarded by swift heavy ions (SHI). Detail understanding of the basic processes of materials modification by SHI will help to construct materials with preassigned properties. Tracks were examined like a chain of deal spherical regions; it was assumed that each incident ion creates one such chain. In this model, we assume that the track is formed randomly, but in that place of the ion path, where the energy value, which loses each ion to the unity of the way, is above some threshold value. As a result of irradiation the number of tracks will continue to grow, areas of the single tracks modified substance continue to overlap, form of modified matter becomes more complicated, creating branched structure. Based on the scaling hypothesis large-scale curve were constructed, critical exponents for this percolation model was established. Two such curves were evaluated: in the case of non-equiprobable distribution of tracks regions in depth with ratio of critical exponents ( / )s 0.68 and in the case with equiprobable distribution of tracks regions in depth, so-called model of continuous percolation with ratio of critical exponents ( / )e 0.41. Differences between critical exponents of this model and the continuous percolation model indicate that the dependence of the modified structure area on the dose and the angle related with the correlation between individual tracks. It results in next effect: angular dependence of the surface area of the branched structure has maximum value at certain «critical» angle of ions incidence.http://jnep.sumdu.edu.ua/am2013ai201

The evolution of the nanoscale dissipative structures in a distribution of defects within the isothermally irradiated f.c.c. crystal

A kinetic model for the influence of external noises such as fluctuations of the vacancies’ generation rate and inhomogeneity of irradiated f.c.c. crystal on the formation of nanoscale modulated dissipative structure in a spatial distribution of vacancies is considered. The generation rate of vacancies all over the sites and a density of their dislocation-type sinks are modelled as independent random uniform stationary fields and with certain defined parameters of fluctuation correlations— spatial and temporal ones. Such stochastic fields can induce a spatial redistribution of vacancies that can lead to their density stationary uniform field or stochastic one. By the average value and correlation functions of these fluctuations, the conditions are determined for interacting fluctuations of the vacancies’ density, under which this homogeneous random field becomes unstable in relation to the stochastic field with a spatially periodic mean distribution of vacancies’ density. For instance, with f.c.c. nickel as a model of the irradiated functional material, the temperature dependence of spatial period d(T) of the modulated dissipative structure of vacancies’ subsystem in f.c.c. crystal is numerically forecasted and analysed, taking into account the total (‘electrochemical’ + ‘straininduced’) interaction between vacancies. Such d(T)-dependence is also determined by the kinetic characteristics of vacancies’ redistribution.The Ministry of Science and Technology, Koreahttp://www.tandfonline.com/loi/tphm202015-05-30hb201