Electronic structure and zone-center phonon modes in multiferroic bulk BiFeO3

Abstract

We present ab initio investigations of the electronic structure and zone-center phonon modes in bulk BiFeO3 with rhombohedral R3c symmetry. The electronic structure has been studied using the plane wave pseudopotential method, with electron-electron interaction treated within the local spin density approximation (LSDA), a spin-polarized generalized gradient approximation (sigma GGA), and the LSDA+U and sigma GGA+U schemes. It is found that with a reasonable choice of a rotationally invariant value of U both the LSDA+U and sigma GGA+U schemes produce electronic band gaps in the range of values derived from optical spectroscopy. The computed electronic structure results are utilized to determine the zone-center phonon modes by applying a linear response technique. We provide a clearer analysis of the energy values and polarization characteristics of the Raman active modes than is presently available from theoretical and experimental studies. (C) 2008 American Institute of Physics.