Revisiting density functionals for the primitive model of electric double layers.

Area of Science:

• Computational chemistry
• Physical chemistry
• Materials science

Background:

• Density functional theory (DFT) is crucial for modeling multi-body systems using one-body density distributions.
• Approximate DFT functionals often lack rigorous theoretical justification and can lead to thermodynamic inconsistencies.
• Validating new DFT functionals requires extensive comparison with molecular simulation data.

Purpose of the Study:

• To systematically compare different density functional versions for ionic distributions near charged surfaces.
• To assess the impact of thermodynamic sum rules on DFT accuracy in electrochemical systems.
• To investigate the sensitivity of DFT performance to functional forms and parameter spaces.

Main Methods:

• Utilized the primitive model of electric double layers for simulations.
• Performed systematic comparisons of various density functional approximations.
• Incorporated statistical-mechanical sum rules into the DFT framework.

Main Results:

• DFT functional performance is highly sensitive to functional form, parameter space, and the specific properties evaluated.
• Approximate functionals can violate statistical-mechanical sum rules, leading to thermodynamic inconsistencies.
• Integrating thermodynamic sum rules into DFT calculations demonstrably improved accuracy.

Conclusions:

• The theoretical performance of DFT functionals in electrochemical systems is nuanced and depends on multiple factors.
• Adherence to thermodynamic sum rules is critical for developing reliable DFT functionals.
• DFT calculations incorporating sum rules offer enhanced accuracy for predicting electrochemical properties and ionic distributions.