Ti metal was investigated by Raman spectroscopy for pressures up to 46 GPa. The E2g mode of the hcp phase shows no softening on approaching the transition to the ω phase, which contrasts the behavior of its heavier homologue Zr, however, it exhibits an anomalously low mode Grüneisen parameter. It is shown that this unusual behavior is also reflected in the pressure response of elastic modulus C44. At ambient conditions the contributions to the temperature shift of this mode due to thermal expansion are one order of magnitude smaller than the explicit contribution. The E2g mode of the ω phase exhibits a positive frequency shift with an ambient pressure mode Grüneisen parameter γ2, slightly higher than that of Zr, becoming smaller under compression. Predictions of a recent first principles calculation, limited to normal pressure and in quite good agreement with experimental data for hcp Ti, underestimate the frequency of the E2g mode of the ω phase by 17%.
|Physical Review B - Condensed Matter and Materials Physics
|Published - Sept 25 2006
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics