The behavior of crowdions and their complexes in weakly stable states of materials

Using the method of molecular dynamics, both single crowdions and their complexes are investigated in an fccmaterial being in a low-stability state with respect to an external thermal force. The system’s state with single crowdions is shown to be weakly stable, and their complexes therefore present a more favorable interstitial position. It is established that even under moderate external action (thermal activation or propagation of a standing wave) single crowdions form a dumbbell defect. In a low-stability state that is developed in the vicinity of structural-phase transformations, it is the crowdion complexes which represent more stable configurations. In addition, the bulk crowdion complex appears to be most favorable, being virtually unaffected by the phonon friction.     

Excitation of gap discrete breathers in an A<Subscript>3</Subscript>B crystal with a flux of particles

The generation of discrete breathers in an A₃B crystal has been modeled by the method of molecular dynamics using Pt₃Al as an example via the application of random unidirectional momenta, which simulate the action of a particle flux, to atoms. Two possible mechanisms of the excitation of gap discrete breathers with a soft type of nonlinearity have been revealed depending on the energy of particles in a flux. If a particle is able to transfer energy of more than 1.4 eV to the Al atom, a discrete breather can be excited by the only particle. Otherwise, a discrete breather is formed upon numerous particle–Al atom collisions, which are possible only at a sufficiently high density of particles, as each following particle must transfer its momentum to the Al atom before its oscillations provoked by previous particles attenuate.     

Excitation of Soliton-Type Waves in Crystals of the A3B Stoichiometry

Physics of the Solid State - Using the method of molecular dynamics and taking Ni3Al and Pt3Al as examples, crystals of the A3B composition are considered for the possibility of excitation of...     

Spatially Localized Oscillations in Low-Stability States of Metal Systems

Russian Physics Journal - An analysis of spatially localized and time-periodic vibrational modes (discrete breathers – DBs) is carried out. It is found out that the discreteness and...     

The Influence of Interstitial Carbon and Oxygen on Grain Boundary Diffusion in Nickel and Silver

Russian Physics Journal - The paper investigates the influence of interstitial carbon and oxygen atoms on their diffusion along the &lt;111&gt;, &lt;100&gt; and &lt;110&gt;...     

A practical crystallographic algorithm for determining the distribution of spatial polyhedra among coordination spheres

We propose a method for determining the population of atoms (sites) on the coordination spheres in fcc crystals. It is shown that only seven spatial polyhedra, containing 6, 8, 12, 24, 24, 24, and 48 vertices may be chosen as a basis for the characteristics of coordination sphere filling. A number of spheres may be represented as a superposition of spatial polyhedra and the coordination number is the sum of the vertices of all the basis polyhedra. The method may be implemented as an automatic process to search for neighbors in any coordination sphere. The basis polyhedra proposed — regular and semiregular Platonic and Archimedic figures — are duals of simple forms which correspond to the symmetry classes considered.Polytechnic Institute, Altay. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 11–15, July, 1992.