Electron Transport through Nanoconfined Ferrocene Solution: Density Functional Theory─Nonequilibrium Green Function Approach

Abstract

We investigate the transport of electrons in a ferrocene aqueous solution nanoconfined between two Pt electrodes using density functional theory and a nonequilibrium Green function method. The system consists of three characteristic phases: metal electrodes, the electrode–solution interface, and the nanoconfined solution phase. By performing the geometry optimization of such systems, it is found that the molecular configuration of water molecules at the Pt surface is adjusted due to the Pt–water interaction, and the charges at the Pt surface are redistributed. Next, by applying the external bias potential via the effective screening medium method during ab initio molecular dynamics simulations, it is revealed that water molecules are packed at the Pt–water interfacial region, and the electrostatic potential profile in the water phase is significantly changed due to aligned water layers. From the analysis of the electron transport characteristics, it is discovered that the ferrocene molecule generates a strong transmission function near the Fermi level and high electron density of states spatially connecting both electrodes through the water phase. These features explain the drastic enhancement in electrical current–voltage characteristics. Therefore, it is concluded that ferrocene enhances electron transport through nanoconfined solutions, indicating that it can be used as a signaling molecule in nanoscale systems for electrochemical sensor applications.

Enabling Ab Initio Molecular Dynamics under Bias: The CP2K+SMEAGOL Interface for Integrating Density Functional Theory and Non-Equilibrium Green Functions

“…In recent years there have been many new implementations of DFT-NEGF in popular DFT packages; 8,10−19 however standard calculations of transport properties are performed at fixed atomic positions and applications to dynamic condensed phase systems remain rare. 20 In this work, we present a new interface between the NEGF code SMEAGOL and CP2K, a popular DFT software package optimized for condensed phase molecular dynamics simulations. 21 We demonstrate that it is possible to perform large-scale molecular dynamics simulations under realistic operating conditions using the DFT-NEGF approach, to the best of our knowledge the first such calculations to be performed.…”

“…In recent years there have been many new implementations of DFT-NEGF in popular DFT packages; ,− however standard calculations of transport properties are performed at fixed atomic positions and applications to dynamic condensed phase systems remain rare . In this work, we present a new interface between the NEGF code SMEAGOL and CP2K, a popular DFT software package optimized for condensed phase molecular dynamics simulations .…”