First-principles calculation of electric enthalpy at voltage-applied electrochemical interfaces

Abstract

In this dissertation, we present a method for calculating the electric enthalpy of a system and its application to an electrochemical interface within the multi-space constrained-search density functional theory (MS-DFT) framework we have recently developed. For the purpose of understanding existing non-equilibrium calculation methods, we perform first-principles based non-equilibrium Green’s function (NEGF) calculations to analyze complex electrostatic properties within nanodevices and further discuss the novel negative differential resistance (NDR) mechanism. Next, in the process of further developing the MS-DFT, an electron occupation rule in the non-equilibrium channel region is established to analyze the quasi-Fermi level (QFL) of molecular junctions in a first-principles manner. In particular, we establish the correlations among the splitting of QFLs, electrostatic potential drops, and Landauer residual-resistivity dipole distribution. Finally, the methodologies for calculating electric enthalpy, including the potential energy of dipole moments in a finite electric field caused between two biased electrodes, are then established based on the well-defined non-equilibrium total energy within MS-DFT. Applying to metal-water interfaces, we calculate the non-equilibrium binding energy of a water molecule to the electrified electrode surface as well as electronic structures of metal-water interfaces, providing first-principles insights into the interfacial water properties on the electrified electrode surface.