High-pressure Raman investigations of phase transformations in pentaerythritol (C(CH2OH)4)

Our high-pressure Raman scattering experiments on pentaerythritol (C(CH 2 OH) 4 ) show that this compound undergoes at least three phase transformations up to 25 GPa. Splitting of various modes at ∼6.3, ∼8.2 and 10 GPa suggests that these phase transformations result in lowering of crystalline symmetry. A very small discontinuous change in slope of most of the Raman-active modes is observed at 0.3 GPa. However, no other signature of a phase transition was observed at this pressure. The observed correlation of the pressures for the onset of the two phase transformations with the limiting values of the distances between various non-bonded atoms in the parent phase suggests that the molecular rearrangements across the phase transformations are not very drastic. In addition, our earlier Fourier transform infrared and present Raman investigations indicate that high-pressure compression leads to increase in strength of the hydrogen bond present in this compound.