High-Pressure Vibrational Studies of HCP Metals by Raman Spectroscopy

The pressure response of Raman phonons, determined for several hcp metals, includes positive pressure shifts as well as anomalies like mode softening in connection with phase transitions. It is shown that the phonon frequencies and their pressure dependences are related to macroscopic elastic parameters. More general, these results show that the measurement of Raman-active phonons in metals provides a direct probe of bonding, and agreement with theoretical models gives additional confidence in ab initio techniques.