Atomistic simulations of helium behavior in tungsten crystals

Based on ab initio calculations, two new pair potentials for He–W have been developed depending on two different W–W potentials in order to investigate the helium behavior in tungsten matrix. These potentials are able to reproduce the correct order of stability for interstitial He in tungsten, overcoming the shortcomings of He–W empirical potentials currently available. We show that different W–W potentials have a significant influence on the He defect properties. Using these potentials, we investigate in detail the diffusion behavior of He in W. An Arrhenius fit to helium diffusion data gives a reasonable migration energy at a value between the experimental data and the ab initio calculations. The different diffusion mechanisms for the two sets of potentials are revealed. The non-Arrhenius diffusion behavior of helium in the tungsten bulk is observed at elevated temperatures over 650 K, which arises from the coexistence of multiple diffusion mechanisms.