Multiple structural transformations in Lennard-Jones clusters: generic versus size-specific behavior.

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Understanding phase transitions in finite systems like atomic clusters is crucial for bridging molecular and bulk properties.
• Lennard-Jones clusters provide a fundamental model for studying phase behavior due to their well-defined interatomic potentials.

Purpose of the Study:

• To construct a size-temperature phase diagram for Lennard-Jones clusters (LJn) up to n=147.
• To identify and characterize generic phase transitions and size-specific behaviors in these clusters.

Main Methods:

• Utilized the exchange Monte Carlo method to compute heat capacities and orientational bond order parameter distributions.
• Analyzed computed data to identify phase transitions and characterize cluster structures.

Main Results:

• Established two generic phase transitions marked by heat capacity peaks: a lower-temperature overlayer melting (Mackay-anti-Mackay) and a higher-temperature core transition.
• The higher-temperature transition involves core melting for three-layer clusters and breaking of icosahedral symmetry for two-layer clusters.
• Observed pronounced size-specific behaviors, particularly in clusters with symmetric global minima, such as a solid-solid transition in LJ135.

Conclusions:

• The constructed phase diagram reveals universal and size-dependent melting behaviors in Lennard-Jones clusters.
• Distinguishes between overlayer and core transitions, highlighting the role of atomic packing and symmetry.
• Provides insights into the fundamental mechanisms of phase transitions in nanoscale systems.