A comparative study of NbAl₃ and Nb₃Al intermetallic compounds under pressure

The effects of pressure on the structural, electronic and mechanical properties of tetragonal NbAl₃ and cubic Nb₃Al have been investigated using first-principles density functional theory approach within the generalized gradient approximation. The calculated structural parameters of two compounds were in good agreement with previous theoretical and experimental data, which linearly decreased with the increasing pressure. The electronic properties of two compounds under pressure have been analyzed. The enhanced covalence under pressure was found due to the increased hybridization between Nb-4d and Al-3p states. The independent elastic constants and mechanical properties have been calculated under pressure. We found that the pressure had a very important influence on mechanical properties. Finally, the ductile/brittle character and mechanical stability of two compounds have been discussed.