FINITE-SIZED ATOMISTIC SIMULATIONS OF SCREW DISLOCATIONS

The interaction of screw dislocations with an applied stress is studie d using atomistic simulations in conjunction with a continuum treatmen t of the role played by the far-field boundary condition. A finite cel l of atoms is used to consider the response of dislocations to an appl ied stress and this introduces an additional force on the dislocation due to the presence of the boundary. Continuum mechanics is used to ca lculate 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 calcul ated for screw dislocations in several close-packed metals. As a concr ete example of the boundary force method, we compute the bow-out of a pinned screw dislocation; the line tension of the dislocation is calcu lated from the results of the atomistic simulations using a variationa l principle that explicitly accounts for the boundary force.