The Effect of Hydrogen, Vanadium and Vacancies on the Properties of Face-Centered Cubic Titanium: Ab Initio Study

The effects of hydrogen, vanadium and vacancies on the structural and energetic characteristics of the face-centred cubic titanium phase are studied using ab initio modelling. It is shown that the introduction of vanadium moderately affects the lattice constants and the bulk modulus, decreasing the cell volume and enhancing the rigidity of the structure. Hydrogen is found to preferentially occupy octahedral sites with a solution enthalpy of –0.67 eV, which is 0.13 eV more favourable than the location in tetrahedra. The influence of vacancies appears as a local weakening of interatomic bonds and a decrease in the bulk modulus. A comprehensive analysis of hydrogen–vacancy, hydrogen–vanadium and vacancy–vanadium interactions shows that the nature of these interactions strongly depends on the local environment of defects. The results for ternary complexes (hydrogen–vacancy–vanadium) are especially interesting: it is shown that the presence of vanadium in the second sphere strengthens the bond between hydrogen and the vacancy. The data obtained provide a deeper understanding of titanium's behavior during thermal hydrogen treatment and vanadium alloying, which is essential for creating strong and heat-resistant alloys of a new generation.