High-Pressure Polymorphs Nucleated and Stabilized by Rational Doping under Ambient Conditions

Area of Science:

• Crystallography
• Materials Science
• Chemical Physics

Background:

• High-pressure polymorphs are often unstable at ambient pressure.
• Doping with larger molecules can induce strain, stabilizing high-pressure phases.
• Understanding phase diagrams is crucial for materials design.

Purpose of the Study:

• To investigate the stabilization of high-pressure polymorphs using dopants.
• To map the pressure-temperature (p-T) phase diagram of resorcinol.
• To elucidate the role of hysteresis in polymorph formation.

Main Methods:

• High-pressure isothermal and isochoric recrystallizations.
• Doping experiments with resorcinol and imidazole derivatives.
• Analysis of crystal structures and phase boundaries.

Main Results:

• High-pressure resorcinol polymorphs (ε and ζ) were stabilized at ambient pressure.
• The p-T phase diagram of resorcinol revealed four polymorphs (α, β, ε, ζ) within 1 GPa.
• Significant hysteresis (up to 5 GPa) was observed during compression of ambient polymorphs, hindering high-pressure phase formation.
• Polymorph ζ, a layered structure, was identified as the only resorcinol polymorph with hydrogen-bonded layers.

Conclusions:

• Doping is an effective strategy for stabilizing high-pressure polymorphs.
• Recrystallization provides a clearer view of the resorcinol phase diagram compared to direct compression.
• Hysteresis in hydrogen-bonded networks significantly impacts polymorph accessibility.