Crowdion presents an interstitial mobile defect propagating in close-packed crystallographic directions and plays an important role in energy and mass transfer processes occurring in bcc tungsten lattice in non-equilibrium conditions. In the present day, tungsten remains one of the most promising plasma-oriented material, which saves its protective features even under high-intensive irradiation influence in nuclear reactors. Crowdions can be one of most possible and effective nonlinear channels of energy dissipation obtaining under irradiation. The dynamics of the crowdion in the lattice with the zero or very low temperature has been already deeply studied. At the same time, influence of thermal oscillations of atoms on the crowdion dynamics has not been studied in detail, despite the processes of irradiation always occur under finite nonzero temperature. In the present work, we try to reveal changing the crowdion features under different finite temperature of the tungsten lattice.
Crowdion as one of types of an interstitial mobile defect propagating in close-packed crystallographic directions can play an important role in relaxation processes occurring in bcc lattices of tungsten in nonequilibrium conditions. The crowdions is an effectively transport of mass and energy in the metal. Tungsten is considered one of the best options as a plasma-oriented material which can be exposed to ion irradiation in nuclear reactors. Recently dynamics of crowdions has been extensively studied for different types of lattices and dimensions. However, the point of energy exchange between crowdions has not been considered earlier. The paper presents an analysis of energy exchange in a complex of crowdions located in neighboring closely packed atomic row. Obtained results reveal that closely located crowdions can intensively transfer energy from one to another thus affecting the dynamics and scenario of defect structure evolution in the crystal. It is known that irradiation of tungsten can lead to microstructural changes, such as bubbles, pores and another types of defects. Moreover, the metal constantly at these conditions are heated up to extremely high temperature. Apparently, the crowdions play an important role in the formation of different defects inside the tungsten. And aim of this work is a numerically analysis of features of the crowdion in this highly heated metal bcc lattice.
A beam of single-layer carbon nanotubes (CNTs) subjected to a shock load in the transverse direction was studied using a chain model with a reduced number of degrees of freedom. The compression shock wave is initiated by a piston moving at a constant speed. Two different scenarios of shock wave propagation and their influence on the structure of the CNT beam depending on the piston velocity were found. At lower speeds, only a faster wave front propagates, which leads to elliptization of the CNT, whereas at higher speeds this is accompanied by a slower wave front of collapse. The evolution of the CNT beam structure in time during compression is studied in detail. The energy absorption rate is estimated as a function of the piston velocity. The results obtained can be useful in the development of new types of elastic shock absorbers.
Crowdion as one of types of an interstitial mobile defect propagating in close-packed crystallographic directions can play an important role in relaxation processes occurring in bcc lattices of tungsten in nonequilibrium conditions. The crowdions is an effectively transport of mass and energy in the metal. Tungsten is considered one of the best options as a plasma-oriented material which can be exposed to ion irradiation in nuclear reactors. Recently dynamics of crowdions has been extensively studied for different types of lattices and dimensions. However, the point of energy exchange between crowdions has not been considered earlier. The paper presents an analysis of energy exchange in a complex of crowdions located in neighboring closely packed atomic row. Obtained results reveal that closely located crowdions can intensively transfer energy from one to another thus affecting the dynamics and scenario of defect structure evolution in the crystal. It is known that irradiation of tungsten can lead to microstructural changes, such as bubbles, pores and another types of defects. Moreover, the metal constantly at these conditions are heated up to extremely high temperature. Apparently, the crowdions play an important role in the formation of different defects inside the tungsten. And aim of this work is a numerically analysis of features of the crowdion in this highly heated metal bcc lattice.
Crowdion is a variation of an interstitial defect located in closely packed atomic rows, can play an important role in relaxation processes occurring in crystals in nonequilibrium conditions effectively transferring mass and energy. Recently dynamics of crowdions has been extensively studied for different types of lattices and dimensions. However, the point of energy exchange between crowdions has not been considered earlier. The paper presents an analysis of energy exchange in a complex of crowdions located in neighboring closely packed atomic row. Obtained results reveal that closely located crowdions can intensively transfer energy from one to another thus affecting the dynamics and scenario of defect structure evolution in the crystal.
Carbon nanotubes (CNTs) have very high mechanical properties and that is why they are used for making super strong and light yarns, ropes, fillers for composites, solid lubricants, etc. Mechanical properties of CNT bundles have been addressed in a number of experimental and theoretical studies. Development of efficient computational methods for solving this problem is an important step in design of new CNT based materials. In the present study, an atomistic chain model is used to analyse mechanical response of CNT crystal under plane strain conditions. The model takes into account tension and bending of CNT wall and the van der Waals interactions. Discrete character of the model allows description of large curvature of CNT wall and CNT fracture at very high pressure. Equilibrium structures of CNT crystal under biaxial, strain controlled loading are obtained and the potential energy of the structure is decomposed into the energy of valence bonds, valence angles and van der Waals interactions. It is shown that the main contribution to the potential energy comes from the energy of valence angles related to bending of CNT walls. The reported simulation results are in a good agreement with the existing literature. The chain model offered here can be efficiently applied to the analysis of mechanical properties of single-walled or multi-walled CNT bundles under plane strain conditions or, under straightforward modifications, to similar structures made of other 2D nanomaterials.
Discrete kinks in Klein-Gordon equations typically have two equilibrium configurations, an unstable one with maximum potential energy and a stable one with minimal energy. The difference between the kink energies in these two configurations gives the height of the Peierls-Nabarro potential. The maximal gradient of this potential gives the minimum force needed to set the kink in motion. It has been shown that some exceptional, non-integrable discretizations of the Klein-Gordon equation have zero static Peierls-Nabarro potential. An arbitrarily small external force in such models results in kink acceleration. Here several methods that give discrete Klein-Gordon models with zero static Peierls-Nabarro potential will be reviewed. Conservation laws which are satisfied for these discrete equations will be mentioned.
Crowdions being interstitial atoms located in close-packed atomic rows, play an important role in relaxation processes that occur in metals and alloys under severe external influences, effectively transferring mass and energy. Recently the concept of a supersonic crowdion was expanded to an N-crowdion consisting in one dimensional motion of N extra atoms along a closely packed atomic row. In this study, the molecular dynamics method was used to study the motion of 1- and 2-crowdions in the fcc Pt lattice. The N-crowdion was excited by applying similar velocity to N neighboring atoms along a closely packed row. It was established that independently of the initial conditions, the crowdion exhibits quasiperiodic breather dynamics, while the average path length is practically independent of the initial velocity and configuration.
The problem of spatiotemporal pattern formation in the wall of arterial vesselsmay be reduced to 1D or 2D models of nonlinear active medium. We address this problem using the discrete array of non-oscillating (bistable) active units. We show how the specific choice of initial conditions in a 1D model with periodic boundary conditions triggers the self-sustained behaviour. We reveal the core of observed effects being the dynamical formation of localized (few-element size) autonomous pacemakers.
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