On the application of constant electrode potential simulation techniques in atomistic modelling of electric double layers

Abstract

This paper presents a brief overview of molecular simulation techniques utilised to simulate the electrode/electrolyte interfaces. We introduce a simple scheme to perform classical molecular dynamics (MD) simulations at constant electrode potential and show that the original constant potential method that employs Gaussian distributed charges can be modified by adding an energy term proportional to the electrode charge squared while keeping other electrostatic interactions similar to those of point charges. Therefore the scheme shown here can be straightforwardly implemented in most MD simulation codes as it requires no modification of the standard energy and force evaluation routines. The impact of the exclusion of Gaussian cross terms of the electrode–electrode and electrode–electrolyte electrostatic interactions is extensively quantified and compared against the original method allowing us to examine the sensitivity of electric double layer (EDL) simulations to the choice of Gaussian width. This scheme provides accurate predictions of EDL structure, electrode charge density and differential capacitance.

Keywords:

• Molecular simulations
• electric double layer
• constant electrode potential

Acknowledgment

Authors gratefully acknowledge the support from project sponsored by the Army Research Laboratory under Cooperative Agreement Number W911NF-12-2-0023. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of ARL or the U.S. Government. The U.S. Government is authorised to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.