Phase transitions and lattice dynamics in perovskite-type hydride [Formula: see text].

First principles calculations have been used to investigate the structural phase transitions and lattice dynamics in the alloy [Formula: see text]. The density functional perturbation theory and the virtual crystal approximation are employed, within the generalized gradient approximation. Our total energy and formation enthalpy results show that [Formula: see text] undergoes a phase transition from the orthorhombic Pnma phase to the polar R3c one at a lithium concentration of x  =  0.