Effect of impurity carbon and oxygen atoms on the behavior of hydrogen in vanadium in a fusion environment: A first-principles study

Abstract

We have investigated the effect of impurity X (X = C and O) atoms on the behavior of hydrogen in vanadium, which is an ideal structural material for nuclear fusion reactors, by first-principles calculations. We found that (1) in bulk V, the interaction between an interstitial H atom and an X atom is repulsive, and the interaction with O is much stronger than that with C. (2) The X–vacancy (vac) cluster can act as a center for capturing H in V. The C-vac cluster can trap as many as two H atoms, while the O–vac cluster can capture up to four H atoms. (3) C and O impurities can effectively decrease the trapping energy of a single H atom in a vacancy. The H-trapping energies in the C–vac and O–vac complexes are 0.88 eV and 0.46 eV, respectively, both of which are lower than those in the X-free vacancy. (4) Both H–X and X-metal interactions affect the H solubility in V. The above results provide important information for application of vanadium as a structural material for nuclear fusion tokamaks.