Individual ion species chemical potentials in the Mean Spherical Approximation
Johan S Høye1, Dirk Gillespie2
1Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
The Journal of Chemical Physics
|July 1, 2022
Summary
This study presents a complete Mean Spherical Approximation (MSA) formulation for ion chemical potential, improving thermodynamic calculations for charged hard-sphere ions. The enhanced theory offers qualitative improvements and extends applicability to systems near neutrality.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Computational Chemistry
Background:
- The Mean Spherical Approximation (MSA) is a key thermodynamic theory for ion energetics in dielectric media.
- Existing MSA formulations for excess chemical potential omitted individual species terms, focusing only on the mean value.
Purpose of the Study:
- To derive and present a complete MSA formulation for the chemical potential of individual ion species.
- To enhance the accuracy and applicability of MSA theory for ionic systems.
Main Methods:
- Derivation of previously omitted terms within the MSA framework.
- Analysis of the additive contributions to individual chemical potentials.
Main Results:
- A complete MSA formulation for individual ion chemical potential (μᵢ) was successfully derived.
- The new formulation includes a simple additive term, offering a qualitative improvement over prior MSA versions.
- The derivation demonstrates that MSA is valid for systems not strictly adhering to global charge neutrality.
Conclusions:
- The enhanced MSA provides a more comprehensive description of ion energetics.
- This improved theory expands the utility of MSA to a broader range of ionic systems, including those near neutrality.
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