Персона: Воскобойников, Роман Евгеньевич
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Институт ядерной физики и технологий
Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.
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Руководитель научной группы "Математическое и компьютерное моделирование в материаловедении"
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Воскобойников
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Роман Евгеньевич
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- ПубликацияТолько метаданныеMD study of surface collision cascades in nickel(2020) Voskoboinikov, R.; Воскобойников, Роман Евгеньевич© 2020 Elsevier B.V.Collision cascades initiated by fast Ni projectiles with energy E = 5, 10, 15 and 20 keV at the surface of nickel target at temperature T = 100, 300, 600, 900 and 1200 K were studied by molecular dynamics simulations. Representative sampling of 24 surface collision cascades per E,T set was generated to get the statistically reliable number of Frenkel pairs NFP and the fraction of vacancies σvac and self-interstitial atoms (SIAs) σSIA in point defect clusters as functions of the projectile energy and irradiation temperature. It was established that NFP,σvac and σSIA in surface collision cascades in nickel averaged over cascade series with the same E,T are higher than those produced in collision cascades in the bulk of the material under the same simulation conditions. Point defects generated in surface cascades predominantly agglomerate into clusters. Spatial separation of vacancies and SIAs due to the interaction of collision cascades with the free surface is the major driving mechanism responsible for the increased number of NFP,σvac and σSIA produced in surface collision cascades in nickel.
- ПубликацияТолько метаданныеOptimal sampling of MD simulations of primary damage formation in collision cascades(2020) Voskoboinikov, R.; Воскобойников, Роман Евгеньевич© 2020 Elsevier B.V.For a few decades now, molecular dynamics (MD) simulations have been extensively used for studying primary damage formation in collision cascades in materials exposed to fast particle irradiation. Because of the stochastic nature of defect production phenomena, it is vital to model collision cascades in batches with the same set of essential simulation parameters that includes primary knock-on atom (PKA) energy and target temperature in the first instance. No generally accepted practice has been established so far to determine the optimal size of the sampling set of MD simulations of collision cascades. The suggested simple a posteriori sampling set size validation method is based on reviewing the dependence of the average and median number of Frenkel pairs generated in collision cascades on the amount n of simulated cascades in a series with identical simulation parameters. As the average and median number of Frenkel pairs converges with raising n, the optimal sampling set size is determined as a function of the simulation conditions. It is shown how it depends on the PKA energy, irradiation temperature, alloy composition and the interaction of collision cascades with the free surfaces.
- ПубликацияТолько метаданныеStatistics of primary radiation defects in pure nickel(2020) Voskoboinikov, R.; Воскобойников, Роман Евгеньевич© 2020 Elsevier B.V.Molecular dynamics simulations were applied to study radiation damage formation in collision cascades initiated by primary knock-on atoms (PKA) with energy EPKA = 5, 10, 15 and 20 keV in pure nickel at temperature T = 100, 300, 600, 900 and 1200 K. A series of 24 collision cascades per EPKA,T set was simulated to assure statistical reliability of the results. The number of Frenkel pairs, NFP, the fraction of vacancies, σvac, and self-interstitials (SIA), σSIA, in point defect clusters, the average size of vacancy and SIA clusters, Nvac and NSIA, respectively, and the average vacancy and SIA cluster per cascade yield, Yvac and YSIA, respectively, were evaluated as functions of EPKA,T. It is found that NFP∝EPKA under all simulated conditions. Both σvac and σSIA demonstrate similar dependence on EPKA. σvac matches Yvac, while σSIA correlates with NSIA and is affected by SIA diffusivity. Nvac is determined by the irradiation temperature and thermal stability of vacancy clusters. They are stable at T ⩽ 300 K and Nvac∝EPKA, whereas at 600 K ⩽ T ⩽ 900 K, Nvac≈6 and 10, which corresponds to the sizes of regular stacking fault tetrahedra. SIA cluster per cascade yield YSIA∝NFP and therefore ∝EPKA under all simulated irradiation conditions.
- ПубликацияТолько метаданныеMolecular Dynamics Simulations of Surface Collision Cascades in Nickel(2020) Voskoboinikov, R. E.; Воскобойников, Роман Евгеньевич© 2020, Pleiades Publishing, Ltd.Abstract: Collisions cascades initiated by Ni atoms with energies E = 5, 10, 15, and 20 keV on the surface of nickel at temperatures T = 100, 300, 600, 900, and 1200 K were simulated using the molecular dynamics method. To obtain statistically significant values of the number NFP of Frenkel pairs and fractions of vacancies σvac and interstitial atoms σSIA in clusters of point defects as functions of (E, T), representative sampling of 24 collision cascades was generated for all energies of incident particles and irradiation temperatures. It was found that the values of 〈NFP〉, 〈σvac〉, and 〈σSIA〉 averaged over all surface collision cascades with equal (E, T) parameters exceed the corresponding parameters of collision cascades in bulk nickel modeled under identical conditions. Point defects produced in collision cascades on the surface of nickel tend to form clusters. The primary physical mechanism increasing 〈NFP〉, 〈σvac〉, and 〈σSIA〉 in surface cascades is the spatial separation of vacancies and interstitial atoms induced by the elastic interaction of point defects with the free surface.
- ПубликацияТолько метаданныеSimulation of Primary Radiation Damage in Nickel(2020) Voskoboinikov, R. E.; Воскобойников, Роман Евгеньевич© 2020, Pleiades Publishing, Ltd.Abstract: The process of radiation damage formation in collision cascades initiated by primary knock-on atoms (PKAs) with energy EPKA = 5, 10, 15, and 20 keV in nickel at temperatures T = 100, 300, 600, 900, and 1200 K was studied using the molecular dynamics method. To ensure the statistical validity of the results, a series of 24 cascades was modeled for each pair of (EPKA, T) parameters. The simulation results were analyzed to determine the number NFP of Frenkel pairs, fractions of vacancies σvac and interstitial atoms σSIA in clusters of point defects, average sizes of vacancy 〈Nvac〉 and interstitial 〈NSIA〉 clusters, and average numbers of vacancy 〈Yvac〉 and interstitial 〈YSIA〉 clusters produced in collision cascades as functions of the PKA energy and simulation temperature. It was found that the relation 〈NFP〉 = 2 ± 0.9 × E1.1 ± 0.1 ΠBA holds true at all the examined values of (EPKA, T). The functional dependences of 〈σvac〉 and 〈σSIA〉 on EPKA were identical. The dependence of 〈σvac〉 follows that of 〈Yvac〉, while 〈σSIA〉 is governed by 〈NSIA〉 and the mobility of interstitials. The value of 〈Nvac〉 depends on the irradiation temperature and the thermal stability of vacancy clusters. These clusters are stable at T ≤ 300 K, and 〈Nvac〉 ∝ EPKA; at 600 ≤ T ≤ 900 K, 〈Nvac〉 ≈ 6 and 10, which corresponds to the sizes of regular stacking fault tetrahedra. The value of 〈YSIA〉 is proportional to 〈NFP〉 and, consequently, to EPKA in the entire range of PKA energies.
- ПубликацияТолько метаданныеA Study of Primary Damage Formation in Collision Cascades in Titanium(2022) Voskoboinikov, R. E.; Воскобойников, Роман ЕвгеньевичAbstract—Molecular dynamics (MD) simulations were applied to study radiation damage formation in collision cascades initiated by primary knock-on atoms (PKA) with PKA energy EРКА = 5, 10, 15, and 20 keV in α-Ti at T = 100, 300, 600, and 900 K ambient temperatures. A series of 24 collision cascades was simulated for each (EРКА, Т) pair. The necessary sampling set size was justified by a simple a posteriori procedure. The number of Frenkel pairs and the fraction of vacancies, (Formula Presented.), and self-interstitial atoms (SIAs), εi, in point defect clusters were evaluated as functions of (EРКА, Т). It was established that collision cascades in α-Ti are extended along PKA trajectories and tend to split into subcascades. In contrast to other elemental metals with close-packed crystal structure, (Formula Presented.) in collision cascades in α-Ti. Moreover, both (Formula Presented.) demonstrate weak temperature dependence. This is an indirect indication that both vacancy and SIA clusters created in collision cascades in α-Ti are stable in the considered temperature range. © 2022, Pleiades Publishing, Ltd.
- ПубликацияТолько метаданныеMD Simulations of Collision Cascades in α-Ti. The Residual Number of Radiation Defects, Cascade Relaxation Time, and Displacement Cascade Region Morphology(2023) Voskoboinikov, R. E.; Воскобойников, Роман Евгеньевич
- ПубликацияТолько метаданныеMD Simulations of Collision Cascades in α-Ti. Cluster Statistics and Governing Mechanisms of Point Defect Cluster Formation(2023) Voskoboinikov, R. E.; Воскобойников, Роман Евгеньевич