First-principles study of lattice dynamics of LiFePO4

Lattice dynamics of lithium iron orthophosphate (LiFePO4) isostructural with olivine have been investigated using the first-principles calculations taking into account the on-site Coulomb interaction within the GGA + U scheme. Born effective charge tensors, phonon frequencies at the Brillouin zone center and phonon dispersion curves are calculated and analyzed. The Born effective charge tensors exhibit anisotropy, which gives a convincing evidence for the one-dimensional Li migration tunnel along the [010] direction in LiFePO4, which has been proposed by other theoretical calculations and experimental observation. The calculated phonon frequencies at the Gamma point of the Brillouin zone show good agreement with the available experimental observations. (C) 2009 Elsevier B.V. All rights reserved.