Effects of chromium on structure and mechanical properties of vanadium: A first-principles study

Stability and diffusion of chromium (Cr) in vanadium (V), the interaction of Cr with vacancies, and the ideal mechanical properties of V are investigated by first-principles calculations. A single Cr atom is energetically favored in the substitution site. Vacancy plays a key role in the trapping of Cr in V. A very strong binding exists between a single Cr atom and the vacancy with a binding energy of 5.03 eV. The first-principles computational tensile test (FPCTT) shows that the ideal tensile strength is 19.1 GPa at the strain of 18% along the [100] direction for the ideal V single crystal, while it decreases to 16.4 GPa at a strain of 12% when one impurity Cr atom is introduced in a 128-atom V supercell. For shear deformation along the most preferable {110} ?111? slip system in V, we found that one substitutional Cr atom can decrease the cleavage energy (?cl) and simultaneously increase the unstable stacking fault energy (?us) in comparison with the ideal V case. The reduced ratio of ?cl/?us in comparison with pure V suggests that the presence of Cr can decrease the ductility of V.