MetalWalls: Simulating electrochemical interfaces between polarizable electrolytes and metallic electrodes

Abstract

Electrochemistry is central to many applications, ranging from biology to energy science. Studies now involve a wide range of techniques, both experimental and theoretical. Modelling and simulations methods, such as density functional theory or molecular dynamics, provide key information on the structural and dynamic properties of the systems. Of particular importance are polarization effects the electrode/electrolyte interface, which are difficult to simulate accurately. Here we show how these electrostatic interactions are taken into account in the framework of the Ewald summation method. We discuss, in particular, the formal set up for calculations that enforce periodic boundary conditions in two directions, a geometry that more closely reflects the characteristics of typical electrolyte/electrode systems and presents some differences with respect to the more common case of periodic boundary conditions in three dimensions. These formal developments are implemented and tested in MetalWalls, a molecular dynamics software which captures the polarization of the electrolyte and allows the simulation of electrodes maintained at a constant potential. We also discuss the technical aspects involved in the calculation of two sets of coupled degrees of freedom, namely the induced dipoles and the electrode charges. We validate the implementation, first on simple systems, then on the well-known interface between graphite electrodes and a room-temperature ionic liquid. We finally illustrate the capabilities of MetalWalls by studying the adsorption of a complex functionalized electrolyte on a graphite electrode.

Classical Quantum Friction at Water–Carbon Interfaces

“…An obvious limitation of the present model is that it is restricted to describing the substrate as a dielectric, rather than a conductor (or semimetal). In principle, extending the current methodology to classical representations of metallic substrates , should be relatively straightforward.…”

On the key role of electrolyte-electrode van der Waals interactions in the simulation of ionic liquids-based supercapacitors

“…For example, modeling the electrodes using constant potential 20 method is nowadays widely used, as well as, the development of models including explicit polarization for the ions of the electrolyte. 40,41 Yet, this work shows that the intensity of the ionelectrode interactions also has a significant impact on the electrode-electrolyte interface, in particular in the determination of the capacitance. As a consequence, the development of a dedicated force field not only for the electrolyte but also for the electrode is of a particular importance in the simulation of electrolyte-electrode interfaces if one wants to determine the capacitance at a quantitative level.…”

Theory and Simulations of Ionic Liquids in Nanoconfinement

“…Bedrov et al 215 provide an excellent introduction and discussion to polarizable force fields, and we will not discuss these further. Technical aspects connected to the computation of electrostatic interactions using polarizable ions were discussed by Coretti et al 264 We note, however, that good agreement between simulation and experiment was obtained using nonpolarizable models by reparametrizing atomistic force fields, 243,277 as well as using coarse grained models. 210,239,240 The accurate modeling of the dynamic properties is also desirable to reproduce the right times scales associated with the cooperative behavior of RTILs and dynamical processes such as lubrication in nanoscale gaps.…”

“…48,51,116,256,290−293 Recently, it has been implemented in the open-source software package Metalwalls. 264,294 A similar method has been implemented in the well-known LAMMPS simulation package 260 and more recently extended to fully periodic systems. 295 Most recently, Ahrens-Iwers et al 296 developed a package ELECTRODE for LAMMPS for efficient simulations of solid− liquid interfaces using constant potential method, able to deal with heterogeneous and curved electrodes.…”