First-principles investigations on vibrational, thermodynamic, mechanical properties and thermal conductivity of L1₂ Al₃X (X = Sc, Er, Tm, Yb) intermetallics

The lattice dynamics, thermodynamic, mechanical properties and thermal conductivity of L1₂ Al₃X (X = Sc, Er, Tm, Yb) intermetallics have been investigated from first-principles calculations by means of using the VASP code. Our results agree well with the previous experiments and calculations. The phonon dispersion curves and the density of phonon states have been calculated by means of using the PHONONPY code and compared with the experimental results. The four compounds stay dynamically stable in the L1₂ structure. We also calculated the thermodynamics properties and give the relationships between thermal parameters and temperature. The elastic constants of the considered compounds are satisfied with mechanical stability criteria. The related mechanical parameters predict that Al₃Sc has higher hardness than the other three compounds, and four compounds all posses a brittle nature. The mechanical anisotropy is predicted by anisotropic constants A^U and A^Z. The results show that the four compounds are all elastically isotropic. We also calculated the thermal conductivity by means of the Clarke's model and Cahill's model and found that the thermal conductivity of the four intermetallics follows the order: Al₃Sc > Al₃Er > Al₃Tm > Al₃Yb. (paper)