Molecular dynamics simulation of dislocation-void interactions in BCC Mo

Molecular dynamics (MD) and molecular statics (MS) simulations have been performed to simulate the motion of a screw dislocation and its interaction with voids in irradiated body centered cubic (BCC) Mo. Considering the unique non-planar core structures of the screw dislocation in BCC metals, the behavior of screw dislocation motion as a function of temperature and applied shear stress is first discussed. A transition from smooth to rough motion of the screw dislocation is observed with increasing shear stress, as well as a change of dislocation glide plane from {1 1 0} to {1 1 2} with increasing temperature. The interaction of a screw dislocation with nanometer-sized voids observed in both dynamic and static conditions is then reported. The obstacle strength calculated from MS calculations shows a large increase in critical resolved shear stress for void diameter larger than about 3 nm. However, the MD results indicate that the screw dislocation interaction with void occurs via a simple shear mechanism.