Chemical Potential Differences in the Macroscopic Limit from Fluctuations in Small Systems

Area of Science:

• Computational Chemistry
• Chemical Thermodynamics
• Molecular Dynamics

Background:

• Calculating chemical potential differences is crucial for understanding phase transitions and chemical reactions.
• Traditional methods often require large system sizes or complex simulations.
• Small system thermodynamics can deviate from macroscopic behavior, posing challenges for accurate calculations.

Purpose of the Study:

• To develop a new method for computing chemical potential differences of macroscopic systems.
• To utilize fluctuations in small, embedded systems to determine thermodynamic properties.
• To investigate the size dependence of chemical potential differences.

Main Methods:

• Employing the small system method with molecular dynamics simulations.
• Sampling particle number fluctuations in embedded systems to obtain Boltzmann probability distributions.
• Comparing overlapping regions of particle distributions from different systems to compute chemical potential differences.

Main Results:

• The method successfully computes macroscopic chemical potential differences with a 3% relative error for truncated and shifted Lennard-Jones potentials.
• Demonstrated the ability to calculate the size dependence of chemical potential differences.
• Extracted chemical potential differences in the thermodynamic limit.

Conclusions:

• The presented method offers a direct route to calculate macroscopic chemical potential differences from molecular dynamics simulations.
• Provides valuable insights into the size dependency of intensive properties in small systems.
• This approach enhances the accuracy and efficiency of thermodynamic calculations.