Electronic structures and lattice dynamics of ternary intermetallic compounds MAlSi (MÂ =Â Ca, Sr, Ba) at high pressures: A first-principles study

In this paper, first-principles calculations based on density functional theory are used here to investigate the electronic structures and lattice dynamics of ternary intermetallic compounds MAlSi (M = Ca, Sr, Ba) under high pressures. Electronic topological transitions (ETTs) occur at high pressures in CaAlSi and SrAlSi, but not in BaAlSi. A study of the lattice dynamics of CaAlSi and SrAlSi under pressures reveals that the low-lying optical phonon mode softens at H point, but the acoustic phonons harden with the increase of pressure. It is indicated that the ambient-pressure structures of these intermetallic compounds are unstable under high pressure, and new structures should be stabilized.