Pressure induced phase transitions in hydroquinone.

Area of Science:

• Solid-state chemistry
• Materials science under extreme conditions
• Spectroscopic analysis of molecular behavior

Background:

• Alpha-hydroquinone (1,4-dihydroxybenzene) is a molecular crystal with a hydrogen-bonded network.
• Understanding its response to external stimuli like high pressure is crucial for materials science.
• Previous studies may not have fully characterized its behavior above 10 GPa.

Purpose of the Study:

• To investigate the high-pressure phase transitions of alpha-hydroquinone.
• To elucidate the structural and dynamic changes occurring under compression using Raman spectroscopy.
• To characterize the nature of disorder induced at elevated pressures.

Main Methods:

• Raman spectroscopy was employed to probe the vibrational modes of alpha-hydroquinone.
• Experiments were conducted under hydrostatic pressure conditions up to 19 GPa.
• Analysis focused on spectral shifts, band broadening, and changes in peak intensities.

Main Results:

• Two distinct pressure-induced transitions were observed around 3.3 GPa and 12.0 GPa.
• The transition at 3.3 GPa is linked to a reduction in crystal symmetry.
• Above 12.0 GPa, significant broadening of internal mode Raman bands indicates increasing disorder, attributed to hydrogen-bonded cage distortion.

Conclusions:

• Alpha-hydroquinone undergoes significant structural rearrangements under high pressure.
• A transition to a disordered state above 12 GPa is driven by the distortion of its hydrogen-bonded network.
• Raman spectroscopy is effective in identifying phase transitions and disorder in molecular solids.