A simple methodology for analyzing association effects on response functions via Monte Carlo simulations

Area of Science:

• Thermodynamics
• Chemical Physics
• Computational Chemistry

Background:

• Understanding thermodynamic response functions is crucial for fluid behavior analysis.
• Self-associated fluids exhibit complex behaviors influenced by molecular interactions.
• Previous studies have explored these effects using various simulation techniques.

Purpose of the Study:

• To develop a novel methodology for analyzing association effects on thermodynamic response functions.
• To quantify the contributions of monomeric and associated species to thermodynamic properties.
• To investigate the influence of molecular association on isobaric heat capacity and volumetric properties of methanol.

Main Methods:

• Development of a simple methodology based on Monte Carlo simulations.
• Expressing residual energy and volume in terms of monomeric and associated fluids.
• Perturbative approach to calculate thermodynamic response functions.
• Application to OPLS methanol along the 50 MPa isobar (220–1500 K).

Main Results:

• Both monomeric and association contributions significantly influence isobaric heat capacity.
• The association contribution to volumetric properties (temperature and pressure derivatives of volume) is negligible.
• A strong correlation was found between the heat capacity of the monomeric fluid and cluster analysis.
• Results are consistent with previous simulation studies.

Conclusions:

• The developed methodology effectively separates association effects on thermodynamic properties.
• Molecular association plays a critical role in heat capacity but not in volumetric properties of methanol under studied conditions.
• Structural analysis of molecular clusters provides insights into thermodynamic behavior.