Raman modes of the two-dimensional tetragonal polymeric phase of C-60 under high pressure

The effect of high hydrostatic pressure, up to 12 GPa, on the phonon spectr um and the material stability of the two-dimensional (2D) tetragonal C-60 p olymer have been studied by means of Raman spectroscopy in the frequency ra nge 100-2000 cm(-1). A number of Raman modes appear in the spectrum for pre ssures above similar to1.4 GPa, whose intensities increase with pressure. T he pressure coefficients of the majority of the phonon modes change gradual ly to lower values for pressures around 4.0 GPa. The deformation of the C-6 0 molecular cage along with the change of the material to a more isotropic state (as far as its elastic properties are concerned) resulting from the a pplication of high pressure may be causing the observed effects in the Rama n spectra. These effects are reversible upon pressure release and therefore the material is stable in the pressure region investigated. (C) 2001 Ameri can Institute of Physics.