First-principles studying the properties of oxygen in vanadium: Thermodynamics and tensile/shear behavior

Employing the first-principles simulation, we investigate the energetics of oxygen (O) and the influence of O on the mechanical behaviors of vanadium. O atom prefers to occupy the octahedral interstitial site with the solution energy of −4.942 eV. Along the [100] direction, the ideal tensile strength of vanadium doped with an O occupying the octahedral interstitial site is 17.4 GPa, which can be reduced by ∼8.9% compared to 19.1 GPa of pure vanadium. This demonstrates that impurity O has a large effect on the tensile strength of vanadium. We further calculate the generalized fault energies including the unstable stacking energy (γus) and the cleavage energy (γcl) in pure vanadium and O-vanadium system in the most preferable {110}<111> slip system. The cleavage energy can be decreased from 1.705 J/m2 of pure vanadium to 1.681 J/m2 of O-vanadium system and simultaneously the unstable stacking energy can be increased from 0.308 J/m2 of pure vanadium to 0.325 J/m2 of O-vanadium system. The ratio of γcl/γus alters from 5.536 to 5.172 and can be thus decreased by 6.57%. This means that the ductility of vanadium will significantly decrease owing to the appearance of impurity O.