The stress-velocity relation of a single dislocation moving in a 2-D lattice has been studied using interactive molecular dynamic simulations. A hybrid interatomic model potential which couples Lennard-Jones(LJ) potential and the Embedded Atom Model (EAM) potential, is used to include radial and many body interactions. Both parts are assembled by a parameter so that the potential can be changed to describe a pure radial interaction to a strong many body interaction in a continuous way. Setting up a constant-stress scenario, the movement of a single dislocation is tracked from zero velocity state, up to a terminal velocity state. The external stress vs. terminal velocity curves have been obtained in the subsonic regime for different values of the coupling parameter. Non-linear relations are found velocity regime 0.1c t to 0.6c t, where c t is the transverse speed of sound. Results have been analyzed using an augmented Peierls model to seek the connection between atomic scale, continuum variables and the limiting speed of dislocations

The stress-velocity relation of a single dislocation moving in a 2-D lattice has been studied using interactive molecular dynamic simulations. A hybrid interatomic model potential which couples Lennard-Jones(LJ) potential and the Embedded Atom Model (EAM) potential, is used to include radial and many body interactions. Both parts are assembled by a parameter so that the potential can be changed to describe a pure radial interaction to a strong many body interaction in a continuous way. Setting up a constant-stress scenario, the movement of a single dislocation is tracked from zero velocity state, up to a terminal velocity state. The external stress vs. terminal velocity curves have been obtained in the subsonic regime for different values of the coupling parameter. Non-linear relations are found velocity regime 0.1ct to 0.6ct, where Ct is the transverse speed of sound. Results have been analyzed using an augmented Peierls model to seek the connection between atomic scale, continuum variables and the limiting speed of dislocations

Bending induced deformations in single walled carbon nanotubes with zigzag and armchair chirality have been studied computationally using a classical molecular dynamics simulation method. In this the interatomic forces have been described with Brenner's empirical model potential. The results given by this classical model have been assessed by letting the most critical, i.e. the most deformed part, of the nanotube further relax by using a dynamical tight binding simulation method. We find that the empirical potential based approach and the tight binding method reproduce similar deformation patterns when the deformation remains relatively small but at higher levels of deformation the results differ significantly. These comparative simulations indicate that graphene interlayer interaction is an important factor in the behavior of deformed nanotubes.

Mechanisms responsible for the formation of a misfit dislocation in a lattice-mismatched system have been studied using Molecular Dynamics simulations of a two-dimensional Lennard-Jones system. Results show clearly how the strain due to the lattice-mismatched interface acts as a driving force for migration of dislocations in the substrate and the overlayer and nucleation of dislocations in the overlayer edges. Moreover, we observe dislocation reactions in which the gliding planes of dislocations change such that they can migrate to the interface.

The structure of a dissociated edge dislocation in copper is investigated. Attention is given to the structure of the Shockley partials and the equilibrium size of the fault ribbon. The studies are carried out through Molecular Dynamics simulations. The atomic interactions have been modelled through an Embedded Atom Model (EAM) potential. the implementation of which has been specially designed for this study. Our main results show that the equilibrium distance between partials is very sensitive to the type of boundary conditions imposed on the simulated system.

We have studied qualitatively the effect of patterned substrate surface on adatom nucleation using Kinetic Monte Carlo simulations and solid-on-solid model. The inhomogeneity in the activation energies of adatom diffusion was incorporated into the simulations using two models: a) periodic variation of the adatom–substrate interaction energy as a function of the adatom lateral position and b) adding a direction dependent and periodically varying diffusion barrier energy to the adatom diffusion activation energy. The effect of the patterned surface was clearly manifested as a confinement of nucleated islands and, consequently, narrowing the island size distribution. The effect was strong in a narrow temperature range.

Mechanical properties of copper and aluminum have been studied using finite temperature molecular dynamics simulations. Atomic interactions have been described by a many-atom effective medium potential, which takes into account interactions up to third neighbors. The computed elastic constants showed good agreement with experimental data. Encouraged by these results the model was applied to study fracture in copper. Systems with a grain boundary and an initial cut serving as a crack seed have been studied. In the first case, crack nucleation and propagation took place exclusively at the grain boundary. In the second case, dislocation propagation was observed in one of the <110> directions, with a speed of about 60% of the longitudinal speed of sound. For thin systems crack propagation occurred through micro-void coalescence with a speed of about 30% of the Rayleigh wave speed in copper.