Phase transformations in methanol at high pressure measured by dielectric spectroscopy technique

TL;DR

This study investigates phase transformations in methanol under high pressure using dielectric spectroscopy, discovering new solid phases, complex structural changes, and glass formation at specific pressure-temperature conditions.

Contribution

It reports the identification of a previously unknown high-pressure low-temperature phase and details complex structural transformations in methanol at high pressures.

Findings

Discovery of a new high-pressure low-temperature phase of methanol.

Observation of complex structural transformations involving four crystalline structures.

Formation of fragile glass in methanol at high pressure and slow cooling.

Abstract

Dielectric response in methanol measured in wide pressure and temperature range ($P < 6.0$ GPa; 100 K $<T<$ 360 K) reveals a series of anomalies which can be interpreted as a transformation between several solid phases of methanol including a hitherto unknown high-pressure low-temperature phase with stability range $P > $ 1.2 GPa $T < 270$ K. In the intermediate P-T region $P \approx 3.4-3.7$ GPa $T \approx 260-280$ K a set of complicated structural transformations occurs involving four methanol crystalline structures. At higher pressures within a narrow range $P \approx 4.3-4.5$ GPa methanol can be obtained in the form of fragile glass ($T_g \approx 200$ K, $m_p \approx 80$ at $P= 4.5$ GPa) by relatively slow cooling.