Static dielectric response and polar phonons of Ba(Mn1/3Nb2/3)O3 and Ba(Ni1/3Nb2/3)O3 complex perovskites

The electronic structure, static dielectric response, and zone-center lattice dynamics of 1:2 ordered complex perovskites Ba(Mn1/3Nb2/3)O3 and Ba(Ni1/3Nb2/3)O3 are investigated using density functional theory within generalized gradient approximation (GGA) and GGA + U methods. Our results indicate that Ba(Mn1/3Nb2/3)O3 is a typical Mott–Hubbard insulator, while the band gap of Ba(Ni1/3Nb2/3)O3 shows a mixture of charge-transfer and Mott–Hubbard type. The calculated dielectric constants are in excellent agreement with experiments. The IR phonon frequencies and oscillator strengths for these two compounds are also analyzed in detail with the purpose of relating to their electronic structures and dielectric properties.