BiFeO₃ domain wall energies and structures: A combined experimental and density functional theory+U study

We determined the atomic structures and energies of 109, 180, and 71 domain walls in BiFeO₃, combining density functional theory+U calculations and aberration-corrected transmission electron microscopy images. We find a substantial Bi sublattice shift and a rather uniform Fe sublattice across the walls. The calculated wall energies (γ) follow the sequence γ₁₀₉<γ₁₈₀<γ₇₁ for the 109, 180, and 71 walls. We attribute the high 71 wall energy to an opposite tilting rotation of the oxygen octahedra and the low 109 wall energy to the opposite twisting rotation of the oxygen octahedra across the domain walls.