Density-Potential Functional Theoretic (DPFT) Schemes of Modeling Reactive Solid–Liquid Interfaces

Simulating electron transfer at reactive solid-liquid interfaces under constant electrochemical potentials of the constituents (electrons, ions, solvent, etc.) is crucial to understanding the formation, function, and failure of electrochemical devices and beyond. Albeit largely accurate in describing the breaking and formation of chemical bonds at solid surfaces, existing methods based on Kohn-Sham density functional theory (DFT) are unsatisfactory in system consistency, namely, simulating the solid-liquid interface under grand-canonical conditions, as well as in scaling up the simulation due to its high computational cost. Herein, to improve the system consistency and computational efficiency, we develop density-potential functional theoretic (DPFT) schemes out of first-principles, drawing upon ideas of Kohn-Sham DFT, orbital-free DFT, frozen density embedding theory, and tight-binding DFT. The proposed DPFT transforms an all-atom, Kohn-Sham DFT description of the nonreactive electrolyte solution into a coarse-grained, field-based description, while retaining a Kohn-Sham DFT description for the reactive subsystem. As a proof of concept, a one-dimensional, orbital-based DPFT model is presented. To reduce the computational cost further, the solid electrode can be described using orbital-free DFT, resulting in orbital-free DPFT models. On the conceptual level, the physical meaning of potential in DPFT is examined. On the application level, the merits and shortcomings of each scheme are compared. This work lays a theoretical basis for DPFT schemes of modeling (reactive) solid-liquid interfaces.