Raman spectra and the structure of rutile at high pressures

Raman spectra of rutile crystals under hydrostatic pressures to 80 kbar and non‐hydrostatic stresses to 155 kbar are reported. Spectral changes near 35 kbar, previously interpreted in terms of a transformation to TiO 2 II, are shown to represent an intermediate case between the spectra of a very anharmonic material at low pressures and a relatively harmonic material at pressures greater than 50 kbar.