Ahrens-Iwers Ludwig J V, Janssen Mathijs, Tee Shern R, Meißner Robert H
Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg, Germany.
Mechanics Division, Department of Mathematics, University of Oslo, N-0851 Oslo, Norway.
J Chem Phys. 2022 Aug 28;157(8):084801. doi: 10.1063/5.0099239.
Constant potential methods (CPMs) enable computationally efficient simulations of the solid-liquid interface at conducting electrodes in molecular dynamics. They have been successfully used, for example, to realistically model the behavior of ionic liquids or water-in-salt electrolytes in supercapacitors and batteries. CPMs model conductive electrodes by updating charges of individual electrode atoms according to the applied electric potential and the (time-dependent) local electrolyte structure. Here, we present a feature-rich CPM implementation, called ELECTRODE, for the Large-scale Atomic/Molecular Massively Parallel Simulator, which includes a constrained charge method and a thermo-potentiostat. The ELECTRODE package also contains a finite-field approach, multiple corrections for nonperiodic boundary conditions of the particle-particle particle-mesh solver, and a Thomas-Fermi model for using nonideal metals as electrodes. We demonstrate the capabilities of this implementation for a parallel-plate electrical double-layer capacitor, for which we have investigated the charging times with the different implemented methods and found an interesting relationship between water and ionic dipole relaxations. To prove the validity of the one-dimensional correction for the long-range electrostatics, we estimated the vacuum capacitance of two coaxial carbon nanotubes and compared it to structureless cylinders, for which an analytical expression exists. In summary, the ELECTRODE package enables efficient electrochemical simulations using state-of-the-art methods, allowing one to simulate even heterogeneous electrodes. Moreover, it allows unveiling more rigorously how electrode curvature affects the capacitance with the one-dimensional correction.
恒电位方法（CPMs）能够在分子动力学中对导电电极处的固液界面进行计算高效的模拟。例如，它们已成功用于逼真地模拟超级电容器和电池中离子液体或盐包水电解质的行为。CPMs通过根据施加的电势和（随时间变化的）局部电解质结构更新单个电极原子的电荷来对导电电极进行建模。在此，我们为大规模原子/分子大规模并行模拟器展示了一种功能丰富的CPM实现，称为ELECTRODE，它包括一种约束电荷方法和一个热恒电位仪。ELECTRODE软件包还包含一种有限场方法、对粒子 - 粒子粒子 - 网格求解器的非周期性边界条件的多种修正，以及一种用于将非理想金属用作电极的托马斯 - 费米模型。我们展示了这种实现对于平行板双电层电容器的能力，为此我们用不同的实现方法研究了充电时间，并发现了水和离子偶极弛豫之间的有趣关系。为了证明对长程静电的一维修正的有效性，我们估计了两个同轴碳纳米管的真空电容，并将其与存在解析表达式的无结构圆柱体进行了比较。总之，ELECTRODE软件包能够使用最先进的方法进行高效的电化学模拟，甚至允许模拟异质电极。此外，它还能更严格地揭示电极曲率如何通过一维修正影响电容。
