Modeling nonionic aqueous solutions: the acetone-water mixture.

Area of Science:

• Computational chemistry
• Physical chemistry
• Solution theory

Background:

• Accurate molecular models are crucial for understanding solution properties.
• Classical models for water and acetone are widely used but require validation.
• Experimental data for enthalpies, pressure, densities, diffusion coefficients, and Kirkwood-Buff integrals exist.

Purpose of the Study:

• To evaluate classical water and acetone models for molecular dynamic simulations.
• To identify models capable of reproducing key experimental thermodynamic and structural data.
• To investigate the limitations of current models in predicting solution behavior.

Main Methods:

• Molecular dynamic simulations were employed.
• Various combinations of classical water and acetone models were tested.
• Simulations focused on reproducing experimental enthalpies, pressure, densities, diffusion coefficients, and Kirkwood-Buff integrals.

Main Results:

• Most model combinations accurately reproduced enthalpies, pressure, densities, and diffusion coefficients.
• Predicting Kirkwood-Buff integrals required extensive simulation times and showed model-dependent divergence.
• Observed model failures, like phase separation, provided insights into microscopic structures.

Conclusions:

• Classical models are generally suitable for bulk properties but fail for detailed structural aspects like Kirkwood-Buff integrals.
• Simulation challenges highlight the complex interplay between hydrogen bonding, concentration fluctuations, and solute organization.
• Further model development is needed to capture the intricacies of solution microscopic structures.