Computational Amperometry of Nanoscale Capacitors in Molecular Simulations

TL;DR

This paper introduces a novel simulation method combining constant potential electrodes with electric displacement to enable realistic amperometry experiments on nanoscale capacitors, capturing open circuit conditions and dynamic responses.

Contribution

The authors develop a new computational approach that allows simulating polarized electrodes at fixed charge and performing amperometry in molecular dynamics.

Findings

Capacitance decreases with faster electric displacement ramps.

Method enables simulation of open circuit conditions.

Full capacitance observed at low current intensities.

Abstract

In recent years, constant applied potential molecular dynamics has allowed to study the structure and dynamics of the electrochemical double-layer of a large variety of nanoscale capacitors. Nevertheless it remained impossible to simulate polarized electrodes at fixed total charge. Here we show that combining a constant potential electrode with a finite electric displacement fills this gap by allowing to simulate open circuit conditions. The method can be extended by applying an electric displacement ramp to perform computational amperometry experiments at different current intensities. As in experiments, the full capacitance of the system is obtained at low intensity, but this quantity decreases when the applied ramp becomes too fast with respect to the microscopic dynamics of the liquid.