Implicit self-consistent electrolyte model in plane-wave density-functional theory

Abstract

Ab-intio computational treatment of electrochemical systems requires an appropriate treatment of the solid/liquid interfaces. A fully quantum mechanical treatment of the interface is computationally unfeasible due to the large number of degrees of freedom involved. In this work we describe a computationally efficient model where the electrode part of the interface is modeled at the density functional theory (DFT) level and the electrolyte part is represented through an implicit model based on the Poisson-Boltzmann equation. We describe the implementation of the model Vienna Ab-intio Simulation Package (VASP), a widely used DFT code, followed by validation and benchmarking of the implementation. To demonstrate the utility of the implicit electrolyte model we apply the model to study the effect of electrolyte and external voltage on the surface diffusion of sodium atoms on the electrode.PACS numbers:

Orbital hybridization-induced band offset phenomena in NixCd1−xO thin films

“…In the present work, the first-principles calculations have been performed within the framework of spin-polarized density functional theory (DFT) [23,24] as employed in Vienna Ab initio Simulation Package (VASP) [25,26]. The meta-generalized gradient approximation (MGGA) [27] with Perdew, Burke, and Ernzerhof (PBE) parameterization is applied for electronic exchange and correlation functional [28].…”

Practical Considerations for Continuum Models Applied to Surface Electrochemistry

“…This work uses the Vienna ab-initio Software Package [29][30][31] in conjunction with VASPsol. 11,32 Core electrons were modeled with projector augmented wave pseudopotentials, 33 while valence electrons were expanded as plane-waves up to a kinetic energy cutoff of 500 eV. When optimizing bulk platinum to determine the appropriate lattice constant, the Brillouin zone was sampled with a 12 x 12 x 12 γ-centered Monkhorst-Pack 34 k-point mesh.…”

“…Details regarding the implementation of these solvation models can be found in their documentation. 11,32…”

Double layer theory

“…Of course, it can be used for fitting results, but this does not give any scientific insights.The approach of an ion towards an electrode surface is governed by a competition between the chemical or physical forces of the electrode and the change in solvation. The resulting balance depends on all parts of the system, e.g., in aqueous solutions, small univalent cations like Li + or Ag + can approach a metal surface while keeping the major part of their solvation energy, while desolvation makes the approach of larger or multivalent ions difficult [4].It is impossible to construct an analytical or semianalytical double layer theory; attempts like the various forms of modified Poisson-Boltzmann theories [5] have given some insights into the deficiencies of the simple theory, but not led to any quantitative results.At the moment, most approaches start with a DFT-based model for the electrode, which is complemented by a simple model for the solution, such as a version of the modified Poisson-Boltzmann theory [6] or a classical DFT model for the electrolyte [7]. They have the advantage that the whole system is modeled, so that the electrode potential can be defined and its effect on the interface be explored in a consistent, but not necessarily realistic manner.…”

“…At the moment, most approaches start with a DFT-based model for the electrode, which is complemented by a simple model for the solution, such as a version of the modified Poisson-Boltzmann theory [6] or a classical DFT model for the electrolyte [7]. They have the advantage that the whole system is modeled, so that the electrode potential can be defined and its effect on the interface be explored in a consistent, but not necessarily realistic manner.…”