Effect of Hydrogen in a Vanadium Grain Boundary by First Principles

The preferential site, segregation and embrittlement properties of hydrogen (H) in a vanadium (V) &Sgr;3 (111) [110] grain boundary (GB) were investigated by first-principles calculations. The solution and segregation energy of H at different interstitial and substitutional sites are calculated. Energetically, H prefers to occupy the GB space rather than substitutional sites and can segregate to the GB with segregation energy of −0.08 eV. Hydrogen is an embrittler at the GB by producing an embrittlement energy of about 0.41 eV, in agreement with experimental observations. Charge density distributions indicate that there are no strong chemical bonds between an H atom and the adjacent V atoms in the GB, and the presence of H atom weakens the bond strength between surrounding V atoms.