Elastic properties of random L1 _2-Al _3(Sc _(0.5)TM _(0.5)) alloys from first-principle SQSs calculations

摘要

Special quasi-random structures (SQSs) with 32 atoms have been generated to model appropriate supercell structure of pseudo-binary random L1 _2-Al _3(Sc _(0.5)TM _(0.5)) (TM = Y, Ti, Zr, Hf, V, Nb and Ta) alloys. The optimized lattice parameters were in good agreement with the experimental data, and the obtained formation energies showed that all L1 _2-Al _3(Sc _(0.5)TM _(0.5)) alloys were stable from energetic point of view. As the atomic radius of substitution elements TM in the same Period decreased, the values of C _(12) and C _(44) for L1 _2-Al _3(Sc _(0.5)TM _(0.5)) alloys exhibited an overall tendency of increase, implying an enhanced Poisson effect and larger resistance to {100} 001〉 shear. The elastic isotropy of L1 _2-Al _3(Sc _(0.5)TM _(0.5)) alloys was overall lowered and the ductility could be improved. The calculated electronic structure demonstrated that below the Fermi level the hybridization of transition-metal d states with Al p states was reduced with decreasing of atomic radius of substitution elements TM in the same Period, which uncovered underlying mechanism for stability and elastic properties of L1 _2-Al _3(Sc _(0.5)TM _(0.5)) alloys.