Ultrafast dynamic compression of cyclohexane

Abstract

Cyclohexane, a key saturated cyclic hydrocarbon in petroleum, is a prospective molecular framework for energetic materials, making its phase diagram a subject of critical interest. Our work pushes the boundaries by exploring phase transitions under ultrafast (nanosecond timescale) dynamic compression using laser-driven shock and in situ time-resolved Raman spectroscopy in contrast to previous study [Yuan et al., J. Mol. Liq. 363, 119836 (2022)] reporting novel phases in cyclohexane at the millisecond time scale. The evolution of Raman bands under dynamic compression reveals crystallization of the sample to the cubic (solid-I) phase around 0.8 GPa followed by solid-I (cubic) → solid-III (orthorhombic) transition in the pressure range of 1.1-1.7 GPa. On further compression, transitions to solid-IV (monoclinic) and solid-V (triclinic) phases are observed in the pressure ranges of 2.7-4.0 GPa and 4.0-5.8 GPa, respectively. Our static compression experiments, performed up to 27 GPa, reveal similar phase transition behavior, contrasting the existing literature. These findings offer new insights into the stability of different high pressure phases of cyclohexane under extreme loading conditions and highlight its potential as a benchmark material for studying phase transition dynamics in molecular systems.