BaTiO3: Energy, geometrical and electronic structure, relationship between optical constant and density from first-principles calculations

• We calculated the physical and chemical properties of eight BaTiO3 polymorphs.
• The most stable phase is rhombohedral phase (R3m).
• The molecular-orbital bonding has been obtained to analyze optical properties.
• The relationship between n and ρm is n = 1 + 0.199ρm.

We have used first-principles density-functional theory calculations to determine the structural, electronic and optical properties of eight known BaTiO3 phases (Pm3¯m, Amm2, C2221, Pmm2, P4mm, P4/mmm, P63/mmc and R3m). The calculated ground state energies, relative stability and structural parameters of these phases are consistent with the reported theoretical and experimental results. We discuss the band structures, densities of states and chemical bonding of eight phases. Further, we analyze the electron density distributions of cubic BaTiO3 and obtain the molecular-orbital bonding. The optical properties of eight phases have been calculated and the relationships between refractive indices and mass densities have been obtained.