Phase transitions in benzene under dynamic and static compression

Abstract

Phase transitions in liquid benzene under laser shocked conditions are studied using high‐resolution time‐resolved Raman spectroscopic technique. The C‐C ring breathing mode (υ1) of benzene at 993 cm−1 is analyzed to monitor the phase transitions occurring in the Raman spectra during shock wave propagation in the pressure range 1.3–5 GPa. Phase transition from liquid benzene to solid benzene (Phase I) is observed below 1.3 GPa, and above this pressure, another phase transition from Phases I and II occurs. We also performed Raman spectroscopic measurements under static compression employing diamond anvil cell (DAC) to compare the effect of shock wave on benzene with isothermal compression using DAC. In static pressure measurements, the first phase transition from liquid to solid benzene (orthorhombic) occurs at 0.3 GPa, and the second phase transition from benzene I (orthorhombic) to benzene Phase II (monoclinic) occurs at 2.3 GPa, which is higher than that observed in case of shock compression experiments. The observed high‐resolution spectrum enables us to determine the effect of pressure gradient upon the Raman spectrum of benzene in shocked condition. One‐dimensional radiation‐hydrodynamic simulations were performed to corroborate the Raman spectroscopic results under dynamic compression. Simulated spatial profiles of the shock wave propagation in benzene at different delay times are used to explain the observation of multiple Raman modes in the spectral region 990–1020 cm−1. It is understood that different regions of the sample experience distinct pressure due to shock pressure gradient across the sample. The new Raman modes appearing in this spectral region are attributed to the Raman signals due to phase transition and from differently shocked regions of benzene under dynamic compression. The effect of reflected shock wave from benzene‐glass interface manifested in terms of red shifting and intensity enhancement of Raman modes at higher pressure is explained in this study.

Pressure effects on the electrical transport properties of benzene

“…[2][3][4] Among others, the high-pressure behavior of C 6 H 6 has always been a research hotspot, from P. W. Bridgman's classic pioneering study to the present. 5,6 The pressure can change the physical form and lattice structure of C 6 H 6 and lead to a series of phase transitions. Previous Raman and X-ray studies indicated that C 6 H 6 transformed from a liquid crystal phase to a solidified phase I (Pbca) with an orthorhombic structure at 0.07 GPa.…”

“…2–4 Among others, the high-pressure behavior of C 6 H 6 has always been a research hotspot, from P. W. Bridgman's classic pioneering study to the present. 5,6…”

Temperature Dependence of the Entropy and the Heat Capacity Calculated from the Raman Frequency Shifts for Solid Benzene, Naphthalene and Anthracene

“…Very recently, the P-T phase diagram has been constructed to determine the solid, liquid and gaseous states for benzene [32]. Phase transitions in liquid benzene (solid-liquid transition) has been studied by using high-resolution time-resolved Raman spectroscopic technique [33].…”

A Comprehensive Review of High-Pressure Laser-Induced Materials Processing, Part II: Laser-Driven Dynamic Compression within Diamond Anvil Cells

“…The technique has allowed researchers to better understand how lasers interact with matter-and how shock-/pressure-waves travel through materials at high pressures [27,29]. Although multi-stage DACs can achieve pressures greater than 380 GPa, when sample sizes greater than 20 µm across are to be compressed, the LDC-DAC mode is presently the primary means to achieve pressures >> 380 GPa [19,[30][31][32].…”