The phase diagram of benzene has been investigated up to 550 °C and 30 GPa in a diamond anvil cell by Raman scattering. A new triple point at 400 °C and 5 GPa and a new phase of solid benzene, called phase IV, have been located at high temperature. The boundaries have been determined between the following solid phases: (i) benzene II and benzene III; (ii) benzene III and benzene III′. The irreversible chemical transformation line of benzene has been determined and can be divided in three parts leading to three different recovered compounds. The P–T diagram obtained by our experimental results is discussed in comparison with published works.

Experiments have been performed to determine the variations of the peak area for the CH4 and N2 Raman lines along with their frequency shift and broadening, as a function of pressure and density, in the case of an equimolar CH4/N2 gas mixture. A comparison is made between the relative values of the Raman scattering cross sections for the two species and the values of the internal field term, versus density of the mixture, showing that the density dependences of these physical quantities become more dissimilar as density increases. Moreover, the ratio of the peak areas for the CH4 and N2 Raman lines is found to be constant in the entire pressure range used. From a practical point of view, these results for gas mixtures could be useful in quantitative analysis of fluid inclusions in rocks.

No abstract

Nitromethane has been studied as a model of the energetic nitro compounds. The phase diagram has been determined by Raman scattering in the pressure and temperature ranges of 0–35 GPa and 20–350 °C, respectively. Three new solid phases of nitromethane called III, IV, V, and their domain of stability have been located. A first chemical transformation is observed by the disappearance of nitromethane Raman modes and by the irreversible formation of a transparent solid called compound I (CI). A second chemical transformation [compound I–compound II (CII)], at higher temperature than the first one, is observed by the sudden darkening of the sample.

Articles you may be interested in[N(CH3)3H]2ZnCl4: Ferroelectric properties and characterization of phase transitions by Raman spectroscopy Nitromethane has been studied as a model of energetic alphatic nitro compounds. The initiation of the decomposition mechanism of nitromethane in the vicinity of its explosive decomposition pressure conditions has been studied under high static pressure at ambient temperature by Raman spectroscopy. The vibrational modes a (NO 2 ) and, to a lesser degree, s (NO 2 ) show a specific behavior at the solid ͑II͒-solid ͑III͒ 7.5 GPa transition ͑at ambient temperature͒. A comparison of the Raman spectrum of nitromethane-h 3 with new high pressure Raman spectroscopic results for nitromethane-d 3 and nitroethane allows one to characterize the physico chemical behavior of these three compounds in relation to their detonic properties.