Pressure-tuning infrared and Raman spectroscopy of group 14 tetraphenyl compounds.

The effect of high external pressures on the vibrational spectra of the tetraphenyl Group 14 compounds, Ph4M (M = Si, Ge, Sn, Pb), were examined between ambient pressure and 40 kbar with the aid of a diamond-anvil cell. The four compounds displayed similar behaviour as the pressure was increased and a structural transition at approximately 15 kbar, most probably associated with a phenyl ring rotation, was identified in each case. The pressure dependencies of selected vibrational modes were obtained.