INFRARED-SPECTRA OF CRYSTALLINE, GLASSY AND LIQUID METHANOL AT HIGH-PRESSURES

Mid-infrared spectra in the range 400-1800 cm(-1) of methanol samples in diamond anvil cells at ambient temperature and pressures up to ii G Pa are reported. The freezing pressure is confirmed to be 3.6 GPa, and the spectra of the resulting metastable glass are very similar to tho se of the liquid. When maintained at high pressure, the glass spontane ously transforms to an ordered crystalline phase which is stable over the range 3.6 to 11 GPa. Small changes in peak wavenumbers for 14 inte rnal modes as a function of pressure are observed, indicating that dis tortion of the molecules ir; minimal. A slight decrease for the C-O-H bending mode is attributed to charge transfer from the molecular O-H b ond to the strengthening intermolecular hydrogen bond.