High-pressure Raman study of the optic-phonon modes in BeO

The shift with pressure of the transverse optic-phonon-mode frequencies in BeO has been measured up to 20 GPa at 25 K by Raman scattering, using a diamond anvil cell. The mode Gr\"uneisen parameters have been determined from the pressure data and are compared with the systematics observed in III-V and other II-VI compounds. The total energy calculations of Chang and Cohen predict a pressure-induced transition from wurtzite to NaCl-type phase at about 20 GPa. Unfortunately the pressure limit in the present study is inadequate to demonstrate this transition, for it stops just near the predicted transition pressure, and would almost surely require considerable over pressure.