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 (γ_cl) and simultaneously increase the unstable stacking fault energy (γ_us) in comparison with the ideal V case. The reduced ratio of γ_cl/γ_us in comparison with pure V suggests that the presence of Cr can decrease the ductility of V.