First-principles study of substitutional solute and carbon interactions in tungsten

Interstitial carbon and substitutional transition metal(TM) solutes are common impurities in tungsten and tungsten alloys. Yet, despite its important role in affecting mechanical and irradiation performances of tungsten, the interplay between these impurities remains largely unknown. In this work, we performed systematic first-principles simulations to study the interaction between carbon and TM solutes. By calculating related binding energies, we found that interplay between carbon and TM solutes is dominated by elastic interactions, with carbon generally showing attractions to TM solutes. Further, including vacancies in our calculation, we found that all solute–vacancy–carbon complexes are energetically stable with respect to associated point defects. Additional analysis shows that vacancy–carbon binding is generally weakened by TM solutes, while carbon also in turn reduces the binding energy between vacancy and TM solutes. Based on these binding energy results, we, respectively, evaluated the effect of solute and carbon on each other’s diffusion behaviors. We found that Cr and V slightly decrease the carbon diffusivity while other commonly seen TM solutes show little impacts on carbon diffusion, and we also expect carbon to slow down vacancy-mediated TM solute diffusion in tungsten.