%0 Journal Article
%A T N Stanislavchuk
%A D S Middlemiss
%A Jaroslaw S Syzdek
%A Y Janssen
%A R Basistyy
%A A A Sirenko
%A Peter G Khalifah
%A Clare P Grey
%A Robert Kostecki
%B Journal of Applied Physics
%D 2017
%G eng
%N 4
%P 045107
%R 10.1063/1.4995282
%T Infrared-active optical phonons in LiFePO<sub>4</sub> single crystals
%V 122
%8 07/2019
%! Journal of Applied Physics
%X <p><span>Infrared-active optical phonons were studied in olivine LiFePO</span><sub><span>4</span></sub><span>&nbsp;oriented single crystals by means of both rotating analyzer and rotating compensator spectroscopic ellipsometry in the spectral range between 50 and 1400&thinsp;cm</span><sup><span>−1</span></sup><span>. The eigenfrequencies, oscillator strengths, and broadenings of the phonon modes were determined from fits of the anisotropic harmonic oscillator model to the data. Optical phonons in a heterosite FePO</span><sub><span>4</span></sub><span>&nbsp;crystal were measured from the delithiated&nbsp;</span><em>ab</em><span>-surface of the LiFePO</span><sub><span>4</span></sub><span>&nbsp;crystal and compared with the phonon modes of the latter. Good agreement was found between experimental data and the results of solid-state hybrid density functional theory calculations for the phonon modes in both LiFePO</span><sub><span>4</span></sub><span>&nbsp;and FePO<sub>4</sub>.</span></p>