Dislocation-vacancy interactions in tungsten

We systematically investigate the interaction between a monovacancy and various lattice dislocations in body-centered cubic (bcc) metal tungsten by means of atomistic simulations. Two models with a different level of sophistication have been employed for the description of interatomic interactions - the empirical Finnis-Sinclair potential, which is a central-force scheme, and the bond-order potential, which is able to describe correctly unsaturated directional covalent bonds that are crucial for the cohesion and structure of bcc transition metals. Our simulation results show that the vacancy-dislocation interaction depends sensitively on the separation distance and orientation of the two defects. A comparison of the simulation results with the predictions of elasticity theory shows excellent agreement between the two approaches when the separation between the vacancy and the dislocation core is above 0.5 nm. Large deviations from the elastic limit are found at close dis tances, when the vacancy enters the dislocation core.