Communication: Computing the Helmholtz capacitance of charged insulator-electrolyte interfaces from the supercell...

Area of Science:

• Computational materials science
• Electrochemistry
• Physical chemistry

Background:

• Modeling electrical double layers (EDLs) at electrified solid-electrolyte interfaces presents computational challenges.
• Existing methods for calculating Helmholtz capacitance are complicated by net polarization effects in supercell models under periodic boundary conditions.

Purpose of the Study:

• To introduce a novel, simplified formula for calculating the Helmholtz capacitance of charged insulator-electrolyte interfaces.
• To validate the new formula using atomistic simulations and demonstrate its independence from supercell size.

Main Methods:

• Development of a new formula based on supercell polarization at zero electric field (Ē = 0) using standard Ewald boundary conditions.
• Validation through atomistic simulations of charged insulator-electrolyte interfaces.
• Application to molecular dynamics codes employing Ewald summation or its variants for electrostatic interactions.

Main Results:

• The proposed formula accurately calculates the Helmholtz capacitance.
• Results are independent of the supercell size, simplifying model setup.
• The method provides a shortcut, avoiding the need to determine the zero net charge state of the EDL.

Conclusions:

• The new formula offers a more direct and efficient method for computing Helmholtz capacitance in supercell models.
• This approach is broadly applicable to standard molecular dynamics simulations of EDL phenomena.
• The findings facilitate more accessible and accurate modeling of electrified interfaces.