Freezing of Lennard-Jones fluid on a patterned substrate

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Understanding phase transitions is crucial for materials design.
• Substrate interactions significantly influence particle ordering and freezing dynamics.
• Molecular dynamics simulations provide atomistic insights into complex systems.

Purpose of the Study:

• To investigate the freezing behavior of Lennard-Jones particles on a commensurate triangular substrate.
• To identify and characterize intermediate phases during the freezing process.
• To explore the effect of substrate-particle attraction on phase transitions and structural ordering.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Lennard-Jones particles interacting with a patterned substrate were simulated.
• Analysis of structural order parameters and phase transition temperatures was performed.

Main Results:

• An intermediate hexatic phase was observed between liquid and crystal in the first two layers for moderately attractive substrates.
• The liquid-hexatic transition was found to be first-order, while hexatic-solid freezing was continuous.
• Increasing substrate attraction shifted transitions to higher temperatures and widened the hexatic phase range.
• Freezing in the bulk remained a first-order transition.
• Layering near the substrate appeared to decrease bulk structural order, with a prestructural cloud observed.

Conclusions:

• The study demonstrates a complex freezing pathway influenced by substrate geometry and attraction.
• The observed hexatic phase and its behavior challenge conventional understanding of freezing processes.
• Substrate effects extend to the bulk, influencing particle ordering and suggesting a layered freezing mechanism.