Finite Sized Atomistic Simulations of Screw Dislocations

TL;DR

This paper combines atomistic simulations with continuum mechanics to study screw dislocations under stress, accurately accounting for boundary effects to determine dislocation behavior and lattice resistance in metals.

Contribution

It introduces a boundary force method that integrates atomistic and continuum approaches to analyze screw dislocations in finite-sized simulations.

Findings

Calculated Peierls stress for screw dislocations in metals.

Demonstrated the boundary force's impact on dislocation response.

Estimated dislocation line-tension from simulations.

Abstract

The interaction of screw dislocations with an applied stress is studied using atomistic simulations in conjunction with a continuum treatment of the role played by the far field boundary condition. A finite cell of atoms is used to consider the response of dislocations to an applied stress and this introduces an additional force on the dislocation due to the presence of the boundary. Continuum mechanics is used to calculate the boundary force which is subsequently accounted for in the equilibrium condition for the dislocation. Using this formulation, the lattice resistance curve and the associated Peierls stress are calculated for screw dislocations in several close packed metals. As a concrete example of the boundary force method, we compute the bow out of a pinned screw dislocation; the line-tension of the dislocation is calculated from the results of the atomistic simulations using a variational principle that explicitly accounts for the boundary force.