Nanoscience Center, Department of Chemistry, University of Jyväskylä, P.O. Box 35 (YN), FI-40014 Jyväskylä, Finland.
Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14 Building 1590, DK 8000 Aarhus C, Denmark.
J Chem Phys. 2019 Jan 28;150(4):041706. doi: 10.1063/1.5047829.
Properties of solid-liquid interfaces are of immense importance for electrocatalytic and electrochemical systems, but modeling such interfaces at the atomic level presents a serious challenge and approaches beyond standard methodologies are needed. An atomistic computational scheme needs to treat at least part of the system quantum mechanically to describe adsorption and reactions, while the entire system is in thermal equilibrium. The experimentally relevant macroscopic control variables are temperature, electrode potential, and the choice of the solvent and ions, and these need to be explicitly included in the computational model as well; this calls for a thermodynamic ensemble with fixed ion and electrode potentials. In this work, a general framework within density functional theory (DFT) with fixed electron and ion chemical potentials in the grand canonical (GC) ensemble is established for modeling electrocatalytic and electrochemical interfaces. Starting from a fully quantum mechanical description of multi-component GC-DFT for nuclei and electrons, a systematic coarse-graining is employed to establish various computational schemes including (i) the combination of classical and electronic DFTs within the GC ensemble and (ii) on the simplest level a chemically and physically sound way to obtain various (modified) Poisson-Boltzmann (mPB) implicit solvent models. The detailed and rigorous derivation clearly establishes which approximations are needed for coarse-graining as well as highlights which details and interactions are omitted in vein of computational feasibility. The transparent approximations also allow removing some of the constraints and coarse-graining if needed. We implement various mPB models within a linear dielectric continuum in the GPAW code and test their capabilities to model capacitance of electrochemical interfaces as well as study different approaches for modeling partly periodic charged systems. Our rigorous and well-defined DFT coarse-graining scheme to continuum electrolytes highlights the inadequacy of current linear dielectric models for treating properties of the electrochemical interface.
固液界面的性质对于电催化和电化学系统至关重要，但在原子水平上模拟这种界面是一个严峻的挑战，需要超越标准方法的方法。原子计算方案至少需要部分地用量子力学来描述吸附和反应，而整个系统处于热平衡状态。与实验相关的宏观控制变量是温度、电极电势以及溶剂和离子的选择，这些也需要明确包含在计算模型中；这需要具有固定离子和电极电势的热力学系综。在这项工作中，在密度泛函理论（DFT）中建立了一个通用框架，其中在巨正则（GC）系综中具有固定的电子和离子化学势，用于模拟电催化和电化学界面。从多组分 GC-DFT 的全量子力学描述开始，采用系统的粗粒化方法来建立各种计算方案，包括（i）GC 系综中经典和电子 DFT 的组合，以及（ii）在最简单的水平上，获得各种（修正）泊松-玻尔兹曼（mPB）隐式溶剂模型的化学和物理合理的方法。详细和严格的推导清楚地确定了粗粒化所需的近似以及在计算可行性的范围内省略了哪些细节和相互作用。透明的近似也允许根据需要去除一些约束和粗粒化。我们在 GPAW 代码中的线性介电连续体中实现了各种 mPB 模型，并测试了它们建模电化学界面电容的能力，以及研究了部分周期性带电系统建模的不同方法。我们对连续电解质进行的严格和明确定义的 DFT 粗粒化方案突出了当前线性介电模型在处理电化学界面性质方面的不足。
