Thermodynamic and structural properties of methanol-water solutions using nonadditive interaction models

Area of Science:

• Physical Chemistry
• Computational Chemistry

Background:

• Methanol-water solutions are crucial in various chemical processes.
• Understanding their bulk and microstructural properties is essential for accurate modeling.
• Molecular polarization significantly influences solution behavior.

Purpose of the Study:

• To investigate the bulk structural and thermodynamic properties of methanol-water solutions.
• To explore the electronic response of water and methanol in different local environments.
• To analyze the solution microstructure using advanced simulation techniques.

Main Methods:

• Molecular dynamics simulations utilizing novel interaction potentials.
• Charge equilibration (fluctuating charge) formalism to account for molecular polarization.
• TIP4P-FQ and CHARMM-based fluctuating charge potentials for inter- and intra-molecular interactions.
• Analysis of radial distribution functions, cluster analysis, and thermodynamic properties.

Main Results:

• The force field accurately predicts most bulk properties, with minor deviations in excess mixing enthalpies.
• Hydration free energy for methanol is calculated as -5.6 ± 0.2 kcal/mol, close to the experimental value.
• Cluster analysis indicates a bipercolating network structure at concentrations where thermodynamic quantities exhibit extrema.

Conclusions:

• The developed force field offers a reasonable description of methanol-water solutions.
• The bipercolating network structure provides a new perspective on solution microstructure.
• Further refinement of alcohol-water interaction potentials could improve accuracy for specific properties.