Scaled-charge ion force field optimized for individual ion partial molar volumes in water
Year: 2026
Type: article
Abstract: We present an ion partial molar volume force field for common monovalent and divalent ionic species, including Li+, Na+, K+, Cs+, Mg2+, Ca2+, F-, Cl-, Br-, I-, OH-, and H3O+. When combined with the TIP4P/2005 water model, the force field enables quantitative investigations of ion-specific effects in both bulk and interfacial properties. The iPMV force field is developed based on a single guiding principle: the ion-water interaction parameters are optimized such that the experimental partial molar volume of each individual ion at infinite dilution-determined via the ultrasonic vibrational potential method-is reproduced by construction. An exception is made for the hydronium ion, for which we also provide an alternative interface-optimized model. The force field employs a charge scaling factor of 0.75 and adopts the Lorentz-Berthelot combining rules for cross-Lennard-Jones interactions, with specific modifications for divalent cations. A distinctive feature of the iPMV force field is that, despite its straightforward design, a single set of ion parameters consistently reproduces a wide range of experimental properties-from volumetric and interfacial properties to salting-out/in effects and transport coefficients. This robust performance suggests a fundamental correlation between the partial molar volumes of individual ions and the broader physical properties of aqueous electrolyte solutions.
Source: The Journal of Chemical Physics
DOI: 10.1063/5.0343028
Institutions: Okayama University, Muroran Institute of Technology
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,500
OpenAlex ID: W7212298256