First principles study of structural, electronic and optical properties of BiFeO₃ in ferroelectric and paraelectric phases

The structural, optical and electronic properties of BiFeO₃ in ferroelectric and paraelectric phases have been investigated using first principles methods within the generalised gradient approximation based on the density-functional theory. Several magnetic configurations have been considered into our calculation, and the antiferromagnetic state is found to be the ground state in both phases. Electronic and optical properties at the antiferromagnetic state are calculated. The band gap of BiFeO₃ is found to be 1·198 and 0.280 eV for ferroelectric and paraelectric phases. The analysis of the electronic structures of BiFeO₃ in ferroelectric and paraelectric phases indicates that the O-2p electrons hybridise with Bi-3d and Fe-3d electrons, which suggests the presence of covalent bonding contribution in BiFeO₃. The dielectric function, absorption, energy loss function and reflectivity were also calculated to discuss the optical properties. The low reflectivity and negligible absorption indicate that BiFeO₃ is a transparent material in the infrared region.