Insight into liquid polymorphism from the complex phase behaviour of a simple model

TL;DR

This study reveals a richer phase diagram for the Jagla model, identifying new crystalline structures and complex features, challenging previous assumptions about liquid polymorphism and phase boundaries.

Contribution

The paper introduces a comprehensive phase diagram of the Jagla model, discovering new crystalline phases and complex structural features not previously reported.

Findings

Identified a family of new crystalline structures.

Located the new melting line at higher temperatures.

Revealed complex structural features shared with ice VI.

Abstract

We systematically explored the phase behavior of the hard-core two-scale ramp model suggested by Jagla[E. A. Jagla, Phys. Rev. E 63, 061501 (2001)] using a combination of the nested sampling and free energy methods. The sampling revealed that the phase diagram of the Jagla potential is significantly richer than previously anticipated, and we identified a family of new crystalline structures, which is stable over vast regions in the phase diagram. We showed that the new melting line is located at considerably higher temperature than the boundary between the low- and high-density liquid phases, which was previously suggested to lie in a thermodynamically stable region. The newly identified crystalline phases show unexpectedly complex structural features, some of which are shared with the high-pressure ice VI phase.