Evolution of atomic collision cascades in vanadium crystal with internal structure

The formation of radiation-damage regions (radiation-damage cascades) in vanadium crystallites with internal structures (intergrain boundary) has been simulated by the molecular-dynamic method. The interatomic interaction is described within the embedded-atom method. A relatively small number of clusters of intrinsic point defects (vacancies and self-interstitial atoms) are formed both in ideal vanadium crystallites and in crystallites with boundaries after the relaxation of atomic-displacement cascades. The evolutionary character of atomic-displacement cascades is determined in many respects by the presence of extended boundaries in materials. The intergrain boundaries hinder the propagation of atomic-displacement cascades and store many radiation-induced defects.     

A molecular-dynamics study of oscillations of unclosed crystal nanostructures based on bilayer metal films

Behavior of unclosed nanostructures is investigated in the course of their formation from bilayer films of a Ni–Cu system with crystal structure. The investigation is performed on the basis of the molecular dynamics method using a many-body potential of interatomic interaction. It is shown that the edges of an unclosed nanostructure produced from a bilayer metal film can perform free harmonic oscillations. The dependence of the oscillation amplitude of the nanostructure on the size of the initial film is investigated. Optimum geometrical parameters of the initial film are determined in order to form unclosed nanostructures oscillating with maximum amplitude. The results obtained are promising for the development of components for nanodevices of different types and applications.     

Nucleation and Evolution of Plasticity in Nanocrystalline Bcc-Iron under Shear Loading

Russian Physics Journal - Special aspects of nucleation and development of plasticity in nanocrystalline BCC-iron during shear are studied. The mechanisms of plastic deformation playing the key...     

Low-density layer formation and “lifting force” effect at micro- and meso-scale levels

The processes at various scale levels in the contact area of interacting objects under high-energy action will be examined from the viewpoint of mesomechanics. Modeling of contact area at atomic- and meso-scale levels was carried out on the base of discrete computational approach (method of particles). Molecular dynamic method was used at the micro-scale level; movable cellular automata method—at the meso-scale level. The gradient of velocity in areas near the surface leads to formation of low density and fragmented areas. This effect is accompanied by the failure of crystal lattice stability and intensive mixing process at the atomic level. The mechanisms of mass transfer in contact area were discussed. The results allow us to explain a host of experimental data of mechanochemistry such as phase formation at friction surface, alloy formation due to contact interaction under “pressure + shear” loading conditions.     

Nucleation of Plasticity in Alpha-Iron Nanowires

Russian Physics Journal - The paper presents research results of the defect nucleation and propagation in the structure of nanosized iron samples with a perfect body-centered cubic lattice under a...     

Influence of structure defects on behavior of unclosed crystal nanostructures

A molecular-dynamic simulation of the behavior of unclosed nanostructures obtained by self-scrolling of nanosized bilayer Ni–Сu films with different internal structure compositions is performed. In the course of selfscrolling of a nanosized film in the absence of any external action, its edges undergo weak decaying harmonic oscillations. Peculiar effects of the initial film internal structure on the oscillation characteristics are found out. It is shown that by varying the initial film composition or saturating it with structure defects, one can deliberately change the oscillation amplitude or frequency, or both of them simultaneously. The layer composition is changed in such a manner that the geometrical dimensions of the simulated nanostructure remain practically unchanged. The observed peculiarities are appealing for research and development of accessories and hardware for nanodevices of different types and applications.     

MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).