Universality Class of Ion-Intercalation Models

Area of Science:

• Physical Chemistry
• Computational Materials Science
• Electrochemistry

Background:

• The Butler-Volmer relation is a dominant model for intercalation kinetics, accurately predicting polarization curves at moderate overpotentials.
• This model traditionally assumes linear diabatic potential energy surfaces (dPESs), which contradicts findings from ab initio constrained density functional theory (DFT) calculations showing significant non-linearity.

Purpose of the Study:

• To investigate the fundamental assumptions of the Butler-Volmer kinetics and its relationship with the linearity of dPESs.
• To develop a more computationally efficient method for modeling intercalation and adsorption kinetics using DFT.

Main Methods:

• Theoretical analysis proving that Butler-Volmer kinetics belongs to a universal class of models not requiring dPES linearity.
• Utilizing two weak assumptions to establish an approximate symmetry, reducing the number of required DFT calculations.
• Conceptualizing intercalation and adsorption as a spherical object traversing two uniform continua within this universality class.

Main Results:

• Demonstrated that Butler-Volmer kinetics is independent of dPES linearity, belonging to a broader universality class.
• The derived assumptions reduce the computational cost for modeling potential energy surfaces by at least 50%.
• A specific model within this class requires only three DFT calculations, compared to twenty-two in previous literature.

Conclusions:

• The Butler-Volmer kinetics is robust and applicable even with non-linear potential energy surfaces.
• The new theoretical framework significantly enhances computational efficiency for studying intercalation and adsorption phenomena.
• This approach offers a more accurate and resource-effective method for materials modeling in electrochemistry and surface science.