A Raman Spectroscopic Study of Nitromethane up to 350 °C and 35 GPa

Abstract
Nitromethane has been studied as a model of the energetic nitro materials. The liquid - transition line has been established by Piermarini [1] and a first solid - solid transition corresponding to the methyl group rotation locking has been evidenced by Cromer [2]. In order to precise the phase diagram of nitromethane, a study has been performed by Raman scattering in the pressure and temperature range of 0 -35 GPa and 20 - 350°C respectively. From these experimental results three new solid phases of nitromethane called III, IV, V and their stability domain have been located. A first chemical transformation line has been detected by the disappearance of nitromethane Raman modes and by the irreversible formation of a transparent solid (CI). A second chemical transformation (CI - CII), at higher temperature, is observed by the sudden darkening of the sample.