Atomistic simulations of dislocation-grain-boundary interactions in tungsten

Mechanical properties of polycrystalline materials are greatly influenced by the motion of dislocations and their interaction with grain boundaries. While isolated dislocations and grain boundaries can be treated nowadays with high accuracy by electronic-structure methods, simulations of mutual interactions between such extended defects are still beyond the reach of these methods because of too high computational demands. In order to describe processes of such complexity one has to cross the bridge between the electronic-structure calculations and atomistic simulations by coarse-graining the electronic degrees of freedom into many-body interatomic potentials. In our study we investigated several cases of dislocation-grain boundary interactions in the body-centered cubic (bcc) transition m etal tungsten using a bondorder potential (BOP). The BOP is based on the tight-binding theory and therefore able to describe correctly directional covalent bonds which are crucial for the cohesion and structure of bcc transition metals. We will present results of BOP simulations for the interaction between both edge and screw dislocations and a variety of symmetric tilt grain boundaries, and discuss the relation between atomic-level phenomena and macroscopic crystal plasticity.