Al₃Pd₂, a novel intermetallic compound: A first-principles study

The potential crystal structures of Al₃Pd₂ are explored by utilizing the newly developed particle swarm optimization (PSO) algorithm for crystal structure prediction based on first-principles calculations. In addition to the previously proposed phase (t-Al₃Pd₂), a new high-pressure phase for Al₃Pd₂ was found: a C2/m symmetric structure (m-Al₃Pd₂). The calculations of the elastic constants and phonon dispersions demonstrate that the new phase is mechanically and dynamically stable. The enthalpy of the new phase is found to be lower than that of the known t-Al₃Pd₂ phase at an applied pressure of approximately 13 GPa. Furthermore, we also investigated the phase transition energy barrier and the effect of temperature on the phase transition between the two Al₃Pd₂ phases. Based on the predicted bulk and shear moduli, the new phase behaves in a ductile manner, which is the same as the known phase. In addition, the electronic structure and the crystal orbital Hamilton population (COHP) diagrams were also calculated to provide further understanding of the transport and bonding features of the novel phase. - Highlights: • A new C2/m symmetric structure (m-Al₃Pd₂) is uncovered. • The new phase is mechanical and dynamical stable. • The t-Al₃Pd₂ phase may transform into the m-Al₃Pd₂ phase. • Temperature is also beneficial for the formation of the new phase. • The new phase is found to behave in a ductile manner and metallic nature