Interaction of hydrogen with impurities in group IVB metals

The energetics of hydrogen bonding with Group IVB metals and the interaction of hydrogen with impurities of 3$d$-transition and simple metals (Al, Ga, Si, Ge) have been investigated using the projector-augmented-wave (PAW) method within the framework of the density functional theory (DFT). It has been found that the solubility of hydrogen in Ti, Zr, and Hf increases upon their alloying with metals located in the middle of the 3$d$ period. The relationship between the interaction energy of hydrogen with impurities, the lattice distortions, and the electronic structure of the studied systems has been analyzed. It has been shown that impurities do not affect the preferred hydrogen sorption positions in titanium but can change these positions in zirconium and hafnium. The influence of impurities and hydrogen on the electronic structure of metals has been examined. The obtained results have demonstrated that, in the studied metals, the interactions of hydrogen with impurities of 3$d$-transition and simple metals are determined by different mechanisms: the attraction of hydrogen by transition metal impurities is caused by the size effect, whereas the repulsion of hydrogen by simple metals can be associated with the electronic factors.