We report Raman spectra and synchrotron x-ray diffraction measurements of lattice parameters of polycrystalline MgB2 under hydrostatic pressure conditions up to 15 GPa. An anomalously broadened Raman band at 620 cm(-1) is observed that exhibits a large linear pressure shift of its frequency. The large mode damping and Gruneisen parameter indicate the vibration is highly anharmonic, broadly consistent with theoretical predictions for the E-2g in-plane boron stretching mode. The results obtained may provide additional constraints on the electron-phonon coupling in the system.
- GRUNEISEN PARAMETERS