Theory and Practice in Constant Potential Molecular Dynamics Simulations

Understanding electrode–electrolyte interfaces at the molecular level is crucial for further progress in electrochemistry, with numerous practical applications in store for society. Molecular dynamics (MD) is a natural technique of choice for accessing molecular-level detail, and the constant potential method (CPM) enables physically realistic and computationally feasible simulations of large systems between conductive electrodes with a specified potential difference. As such, this review aims to introduce readers to the most important concepts of the CPM, such as dynamic charge updating methods, importance sampling in the constant potential ensemble, and optimal periodic boundary conditions for calculating long-range electrostatic interactions. The CPM has been used to study the capacitance of room-temperature ionic liquid supercapacitors and the relationship with electrolyte layering near charged electrodes, the mechanisms and kinetics of charging and discharging, and the utility of nanoporous electrodes in achieving ionic nanoconfinement and superionic states. These areas highlight the flexibility of CPM MD and the additional physical realism that is achieved over simpler fixed charge methods when studying complex electrolyte–electrode interfaces. Nonetheless, there are many potentially fruitful ways to further optimize CPM MD simulations, alongside numerous areas where the application of this technique could yield novel and interesting results.