Computational Amperometry of Nanoscale Capacitors in Molecular Simulations

In recent years, constant applied potential molecular dynamics has allowed researchers to study the structure and dynamics of the electrochemical double-layer of a large variety of nanoscale capacitors. Nevertheless, it has 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 us 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.

Automated summary

By combining a constant potential electrode with a finite electric displacement, it is now possible to simulate open-circuit conditions for polarized electrodes at fixed total charge. This method can be extended to perform computational amperometry experiments at different current intensities by applying an electric displacement ramp. The full capacitance of the system is obtained at low intensity, but decreases when the applied ramp is too fast compared to the microscopic dynamics of the liquid, similar to experimental results.