First-principles investigation of grain boundary morphology effects on helium solutions in tungsten

Abstract Helium solutions at eight symmetric tilt grain boundaries (GBs) in tungsten (W) have been investigated through first-principles calculations. The GBs are constructed by the coincidence site lattice (CSL) model and all interstitial sites at GBs are identified with convex deltahedra. For each GB, helium atom prefers to dissolve in interstitial sites with the lowest charge density. Interactions between the helium atom and the GBs atoms are rather localized for all eight GBs studied here, and the helium solution explicitly relates to the local environment of the interstitial site. It is found out that the helium solution energies decrease as the Voronoi volumes of interstitial sites increase, and they can be quantitatively determined by helium solution energy in tungsten clusters W n . Based on this quantitative relationship, it is easy to estimate the helium solution energy in various interstitial sites in tungsten without massive first-principles calculations. Our result provides a sound theoretical guide to design favorite grain boundaries to suppress helium segregations at GBs.