Concentration Fluctuation/Microheterogeneity Duality Illustrated with Aqueous 1,4-Dioxane Mixtures

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding aqueous mixtures is crucial for various chemical applications.
• 1-4 dioxane mixtures exhibit complex structural behavior influenced by molecular interactions.
• Simulations are vital for probing molecular-level properties inaccessible through experiments alone.

Purpose of the Study:

• To investigate the structural properties of aqueous 1-4 dioxane mixtures using computer simulations.
• To link molecular-level structural characteristics to measurable properties like radiation scattering and Kirkwood-Buff integrals (KBIs).
• To develop and validate a consistent correction strategy for KBIs derived from simulations.

Main Methods:

• Utilizing computer simulations with various water and 1-4 dioxane force field models.
• Applying a novel strategy for correcting simulated Kirkwood-Buff integrals (KBIs).
• Analyzing the impact of water aggregates and model dependence on mixture structure.

Main Results:

• A reliable method for obtaining genuine KBIs for aqueous 1-4 dioxane mixtures was established.
• Differences in mixture structure were elucidated, highlighting the role of water aggregates.
• The study revealed the model-dependent nature of structural properties, particularly concerning water models like SPC/E and TIP3P.

Conclusions:

• The proposed KBI correction method enables accurate analysis of aqueous mixtures across all concentrations.
• Simulations provide insights into the molecular basis of concentration fluctuations and domain segregation in mixtures.
• These findings are essential for interpreting experimental data, such as X-ray spectra, and understanding mixture behavior.