The effects of dilute concentrations of substitutional Re or Os on the thermodynamics and kinetics of oxygen in tungsten

Tungsten is a candidate material for use in plasma-facing components of fusion reactors. Under operating conditions, transmutation occurs through exposure to neutrons giving rise to rhenium and osmium. Since oxidation is a major operational concern leading to material degradation, it is important to study this issue. In this work, the effects of dilute concentrations of rhenium and osmium on oxygen binding and diffusion in tungsten were investigated using multi-scale modeling. It was determined that the addition of dilute levels of Re or Os (less than 1 at%) led to complex, attractive and long range interactions with the interstitial oxygen. The cases where the interstitial oxygen occupied the 1st, 2nd, and 5th nearest neighboring T-sites were associated with the most favorable binding. Oxygen diffusivity in the material was found to decrease with increasing the substitutional defect concentrations. Finally, osmium was found to have a larger impact on the energy landscape. •The effects of dilute Re and Os on O binding and diffusion in W were analyzed.•The oxygen was found to favor binding to the T-sites.•The introduction of the defect generally led to enhanced oxygen binding.•Osmium a larger influence on the local energy landscape.•Oxygen diffusion was found to decrease with increasing defect concentration.