Efficient electron open boundaries for simulating electrochemical cells

Non-equilibrium electrochemistry raises new challenges for atomistic simulation: we need to perform molecular dynamics for the nuclear degrees of freedom with an explicit description of the electrons, which in turn must be free to enter and leave the computational cell. Here we present a limiting form for electron open boundaries that applies when the magnitude of the electric current is determined by the drift and diffusion of ions in solution, and which is sufficiently computationally efficient to be used with molecular dynamics. We demonstrate its capabilities by way of tight binding simulations of a parallel plate capacitor with and without a dimer situated in the space between the plates.