Phonon calculation on olivine‐like LiMPO₄ (M = Ni, Co, Fe) and Raman scattering of the iron‐containing compound

Abstract

Abstract The phonon properties of the lithium transition metal phosphates LiMPO 4 (M = Ni, Co, Fe) with the olivine structure were studied using a computational simulation. The calculation employs a normal coordinate analysis based on the Wilson's FG matrix method. The method applied to LiNiPO 4 allowed for the fitting of a set of stretching force constants and angle bond strengths that resulted in Raman wavenumbers comparing with experiments within a 5% average deviation. This set was assumed fixed for the isostructural Co‐containing and Fe‐containing compounds, as a first approximation. The calculated LiCoPO 4 Raman wavenumbers also compared well with experimental values (average deviation 9%). Using this procedure, the 36 Raman wavenumbers of LiFePO 4 were predicted and assigned to vibrational motions and symmetry species of the crystal group. LiFePO 4 unpolarized Raman data agree very well with the predicted values. Copyright © 2004 John Wiley & Sons, Ltd.