Mechanics of defect transport in tungsten from first-principles calculations

p, li {white-space: prewrap;} Tungsten (W) is an important material for high temperature applications due to its refractory nature. However, like all transition metals from the VI-A group, W suffers from low-temperature brittleness and lack of ductility, which severely limits its use as a structural material. Tungsten’s mechanical properties can be enhanced by alloying with elements with d-electrons, such as Re, which has resulted in successful commercial alloys. Nevertheless, the underlying mechanisms remain incompletely understood. In this study, we focus on developing an understanding on the formation and migration energetic of Re solute atoms and their interaction with vacancies and dislocations. To explore the infl uence of external stresses on Re transport properties, we examine the role of hydrostatic and shear deformation on the vacancy formation energy and migration energy barrier (Em) in BCC W from fi rst-principles calculations by developing a transferable pseudopotential with 6s2, 6p0, 5d4, and 5f0 electronic states for the valence electrons. We fi nd that under hydrostatic deformation, increase or decrease of vacancy formation energy depends on the type of deformation – tensile or compressive, whereas for shear deformation it decreases irrespective of the magnitude of applied deformation. On the other hand, migration energy barrier always decreases under hydrostatic deformation, but shows path-length dependent behavior under shear deformation. Moreover, the interaction details of a Re atom with edge and screw dislocations display a defi nitive site preference for the solute atoms to bind at the dislocation cores in W and indicate possible mechanisms for enhancing its fracture strength from a fundamental physics perspective.