Grand canonical electronic density-functional theory: Algorithms and applications to electrochemistry.

Area of Science:

• Computational Chemistry
• Electrochemistry
• Materials Science

Background:

• Realistic theoretical modeling of electrochemical systems is crucial for designing new materials and processes.
• Traditional methods struggle with the continuous change in electron numbers during reactions.
• An ensemble approach mimicking experimental conditions is needed.

Purpose of the Study:

• To develop and present novel algorithms for electronic density-functional theory (DFT) calculations in the grand canonical ensemble at a fixed potential.
• To improve the computational efficiency and accuracy of modeling electrochemical reactions.
• To elucidate the mechanism behind the second voltammetric peak in copper deposition on platinum.

Main Methods:

• Implementation of two algorithms: a self-consistent field method and a direct variational free energy minimization method using auxiliary Hamiltonians (GC-AuxH).
• Solving Kohn-Sham equations of DFT directly in the grand canonical ensemble.
• Application of grand-canonical DFT to under-potential deposition of copper on platinum in chloride-containing electrolytes.

Main Results:

• Both developed algorithms show significant performance improvements over conventional fixed-number calculations.
• The GC-AuxH method demonstrates reliable and smooth exponential convergence of the grand free energy.
• The study identified chloride desorption, not copper monolayer formation, as the cause of the second voltammetric peak.

Conclusions:

• The developed grand-canonical DFT methods provide a more accurate and efficient approach for modeling electrochemical systems.
• These methods enable a deeper understanding of reaction mechanisms at electrode interfaces.
• The findings offer new insights into the copper deposition process on platinum surfaces.