Improving Continuum Models to Define Practical Limits for Molecular Models of Electrified Interfaces

Upper panel: Estimates of critical sizes (L) for AIMD of aqueous electrolytes of varying concentration (n), with a snapshot of an AIMD simulation of KF/H2O next to a gold electrode. Lower panel: a) non-monotonic ion profiles (vs. distance from electrode) in the double layer as the potential approaches a reduction level (indicated by arrows), b) ion profiles and electrostatic potential useful for design of AIMD simulations.

Scientific Achievement

We develop a self-consistent methodology for modeling biased interfaces that combines (i) continuum theory and (ii) ab initio molecular dynamics, to explore the structure of the electric double layer under various electrochemical conditions, including effects of electron transfer and non-electrostatic interactions (e.g. adsorption).

Significance and Impact

Ab initio molecular dynamics studies aiming to describe biased interfaces are often computationally limited to small sizes, suffer from inconsistency with boundary conditions (concentration, surface charge, etc.) and large fluctuations that may compromise stability. Here we provide estimates of minimum requirements for a microscopic description in terms of the cell sizes of ab initio molecular dynamics setups and the applied surface charge density/electrode potential.

Research Details

  • The potential-dependent charge distribution in the double layer close to redox levels can be efficiently performed with a formalism based on a pair of coupled modified Poisson-Boltzmann equations
  • For realistic electrolyte concentrations (~1M) and voltages (~0.1V), reliable AIMD simulations can be designed based on a continuum model, avoiding strongly non-equilibrium configurations and incompatibility with the target external conditions

DOI: 10.1149/2.0461711jes

Download this highlight

Latest Updates

See All