First-principles study of octahedral tilting and ferroelectric-like transition in metallic LiOsO3

The octahedral tilting and ferroelectric-like structural transition of LiOsO3 metallic perovskite [Y. Shi et al., Nat. Mater. 12, 1024 (2013)] is studied using first-principles density-functional theory. In LiOsO3, the a a-a octahedral tilting mode is responsible for cubic (Fm(3) over bar m) to rhombohedral structure (R(3) over bar c), which is stable phase at room temperature, and at low temperature, noncentrosymmetric transition to R3c rhombohedral transition is realized as a result of zone center phonon softening. By using density-functional calculation and phonon calculation, the phase transition behavior of LiOsO3 can be fully understood. We also present electronic structure change and Fermi surface change due to electron lattice coupling effect. The change of carrier density of state across phase transition is associated with experimental temperature dependence of resistivity, heat capacity, and susceptibility.