Temperature evolution of infrared- and Raman-active phonons in graphite

We perform a comparative experimental and theoretical study of the temperature dependence up to 700 K of the frequency and linewidths of the graphite E₁ᵤ and E2g optical phonons (~1590 and 1580 cm^-1) by infrared (IR) and Raman spectroscopy. Despite their similar character, the temperature dependence of the two modes is quite different, e.g., the frequency shift of the IR-active E₁ᵤ mode is almost twice as big as that of the Raman-active E2g mode. Ab initio calculations of the anharmonic properties are in remarkable agreement with measurements and explain the observed behavior.