Energetics and diffusional properties of He in BCC Mo: An empirical potential for molecular dynamics simulations

This paper presents an interatomic potential for modeling He defects and bubbles in body-centered-cubic (BCC) Mo. We utilize three existing frameworks: the Finnis–Sinclair (FS) potential for Mo–Mo, the Effective-Medium-Theory (EMT) for He–Mo, and the Hartree–Fock-Dispersion (HFD) potential for He–He interactions. The energetics of He defects and the diffusivity of He interstitial given by this potential agree well with ab initio calculations and experimental measurements. Furthermore, in agreement with theoretical prediction, it is shown that the introduction of He gas suppresses the surface diffusivity of BCC Mo, which decays exponentially with increasing He pressure acting on the free surface. The decay constant, correlated with the characteristic interaction volume for He–Mo, is close to the atomic volume of BCC Mo. This suppression effect is important to understand the mobility of small He bubbles.