Ion-Ion Association in Bulk Mixed Electrolytes Using Global and Local Electroneutrality Constraints.

Area of Science:

• Physical Chemistry
• Solution Chemistry
• Computational Chemistry

Background:

• Ion atmospheres significantly influence interactions in charged solutions.
• A precise understanding of ion atmosphere structure and behavior is currently lacking.
• Accurate modeling of electrolyte solutions is vital for various scientific and industrial applications.

Purpose of the Study:

• To develop and validate a theoretical framework for describing net ion-ion distributions in bulk electrolyte mixtures.
• To establish relationships between local and bulk electroneutrality constraints and ion distributions.
• To elucidate the contributions of ion distributions to both charge neutralization and overall solution thermodynamics.

Main Methods:

• Application of Kirkwood-Buff theory, an exact statistical mechanical theory for mixtures.
• Incorporation of local and bulk electroneutrality constraints.
• Validation through classical explicit solvent molecular dynamics simulations of diverse electrolyte mixtures.

Main Results:

• Established exact relationships between all net ion-ion distribution functions in bulk electrolyte mixtures.
• Demonstrated that ion distributions can be deconvoluted into charge neutralization and thermodynamic contributions.
• Confirmed the universality of these relationships across various ion types, concentrations, temperatures, and pressures.

Conclusions:

• The developed relationships provide a comprehensive description of ion atmospheres in electrolyte solutions.
• The findings offer a pathway to better predict and understand the thermodynamics of solutions based on ion distributions.
• This work is applicable to atomic and molecular ions in any solvent system, advancing the field of solution chemistry.