Size and temperature dependent shapes of copper nanocrystals using parallel tempering molecular dynamics

Area of Science:

• Computational materials science
• Nanotechnology
• Chemical physics

Background:

• Predicting the equilibrium shapes of metal nanocrystals is crucial for controlling their properties.
• Existing models often focus on minimum energy configurations, potentially overlooking temperature and size effects.

Purpose of the Study:

• To investigate the temperature- and size-dependent equilibrium shapes of copper (Cu) nanocrystals.
• To understand the role of vibrational entropy in determining nanocrystal morphology.
• To provide insights for achieving selective nanocrystal shapes in material processing.

Main Methods:

• Parallel-tempering molecular dynamics simulations were employed to explore shape transitions.
• Electronic density functional theory calculations complemented the simulations.
• Simulations covered Cu nanocrystals in the 100- to 200-atom size range.

Main Results:

• Frequent solid-solid shape transitions were observed for Cu nanocrystals with varying temperature.
• Vibrational entropy favors intermediate shapes between decahedra and icosahedra.
• Significant shape variations occur with subtle changes in nanocrystal size, even by a single atom.

Conclusions:

• Entropy significantly influences Cu nanocrystal shapes at experimental temperatures.
• Minimum-energy predictions may not accurately reflect observed shapes.
• Understanding these shape dynamics is vital for targeted nanocrystal synthesis and applications.