Structural properties of methanol-water binary mixtures within the quantum cluster equilibrium model

Area of Science:

• Computational chemistry
• Physical chemistry
• Thermodynamics

Background:

• Methanol-water mixtures are crucial in various chemical processes.
• Understanding the molecular structure and interactions in these mixtures is essential.
• Previous studies have explored their properties using different simulation techniques.

Purpose of the Study:

• To investigate the structural characteristics of methanol-water clusters.
• To calculate thermodynamic properties of methanol-water mixtures using quantum chemical methods.
• To compare theoretical predictions with experimental data.

Main Methods:

• Density functional theory (DFT) with B3LYP-D3 and M06-2X functionals was employed.
• Calculated interaction energies were used in the Quantum Cluster Equilibrium Theory (QCE) framework.
• QCE model parameters were fitted to experimental isobar data for methanol-water mixtures.

Main Results:

• DFT calculations characterized 93 methanol-water clusters of various types and sizes.
• Cubic and spiro cluster motifs were found to be dominant in the mixtures.
• The QCE model, parameterized to experimental data, showed reasonable agreement for excess enthalpies, entropies, and Gibbs free energies of mixing.
• Poor agreement was observed for heat capacities.

Conclusions:

• The study identifies dominant structural motifs in methanol-water clusters.
• Quantum Cluster Equilibrium Theory, combined with DFT, provides a reliable method for predicting key thermodynamic properties of these mixtures.
• Further refinement may be needed for accurate prediction of heat capacities.