Uniaxial-Stress Dependence of the Raman-Active Phonons in TiO2

The uniaxial-stress derivatives of the $B_{1g}$, $E_g$, and $A_{1g}$ Raman-active phonon-mode frequencies of rutile were measured at room temperature. The measurements were combined with previous measurements of the temperature dependences of these three modes to evaluate precisely the anharmonic contributions to the phonon self-energies. Results of the separation of the isobaric frequency shifts of the phonon modes into pure-volume and pure-temperature contributions are compared with similar results based on a cubic approximation. We conclude that the cubic approximation is valid to ∼ 10% for the Raman-active modes in this material.