Effect of a potential softness on the solid-liquid transition in a two-dimensional core-softened potential system

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• Anomalous liquid behavior, such as that of water, is often described using core-softened potentials.
• Understanding phase transitions in two-dimensional (2D) systems is crucial for materials science and statistical mechanics.

Purpose of the Study:

• To investigate the melting behavior of a 2D system with a purely repulsive isotropic core-softened potential.
• To analyze how changes in potential softness influence melting scenarios and phase transitions.
• To explore the applicability of these findings to confined water systems.

Main Methods:

• Molecular dynamics simulations were employed to model a 2D system of classical particles.
• A purely repulsive isotropic core-softened potential was utilized to describe particle interactions.
• System parameters, including potential softness and density, were systematically varied.

Main Results:

• Melting scenarios were found to be highly dependent on the width of the repulsive shoulder in the potential.
• At small shoulder widths, weakly first-order melting transitions were observed.
• At larger shoulder widths, reentrant melting transitions occurred upon compression, and continuous two-stage melting with an intermediate hexatic phase was seen at low densities.
• First-order transitions were identified at high densities.

Conclusions:

• The study demonstrates a rich variety of melting behaviors in 2D systems governed by core-softened potentials.
• The findings highlight the significant impact of potential softness on phase transitions, including reentrant melting and the Kosterlitz-Thouless-Halperin-Nelson-Young scenario.
• Results offer insights into the behavior of water confined between hydrophobic surfaces.