First-principles investigation on the effect of carbon on hydrogen trapping in tungsten

The effects of carbon (C) on hydrogen (H) trapping in tungsten (W) have been investigated by using a first-principles method, C exhibits a weak attractive interaction with H at a distance of ∼2.5 in intrinsic W. H is energetically favorable to be far away from C, and prefers to bind onto an isosurface of an optimal charge density of 0.10 electrons/³ at the vacancy with C. Such optimal charge density region shrinks when more H atoms are added, and disappears with the addition of a sixth H, which bonds strongly with C characterized by a much higher C-H charge density. The presence of C increases the trapping energy of H at the vacancy, indicating a strong effect of C on H trapping in W.