Inverse melting in a two-dimensional off-lattice model.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Inverse melting, where a solid transforms into a liquid upon compression or a liquid into a solid upon heating, is a counterintuitive phenomenon.
• Understanding the conditions and mechanisms driving inverse melting is crucial for designing novel materials and predicting their behavior under varying thermodynamic conditions.

Purpose of the Study:

• To investigate inverse melting in a simple, two-dimensional off-lattice model.
• To explore the influence of particle interaction parameters, specifically the repulsive shoulder and attractive well, on the inverse melting transition.
• To characterize the nature of the phase transition and comment on methods for assessing translational ordering.

Main Methods:

• Utilizing computer simulations of a monodisperse system of core-softened disks.
• Systematically varying potential parameters to observe changes in phase behavior.
• Analyzing the system's response to isobaric heating across a range of pressures.

Main Results:

• Demonstrated inverse melting, where the liquid phase freezes into a crystal upon isobaric heating.
• Identified the extent of the repulsive shoulder as a key parameter controlling the pressure range of inverse melting.
• Confirmed the first-order nature of the melting transition to a crystalline phase, not hexatic or quasicrystal phases, in two dimensions.

Conclusions:

• The study successfully models and demonstrates inverse melting in a 2D system.
• The findings highlight the significant role of specific inter-particle potentials in driving unusual phase transitions.
• The research provides insights into the fundamental physics of melting and crystallization, with implications for materials science.