Nwankwo Udoka, Wang Yi-Di, Lam Chi-Hang, Onofrio Nicolas
Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China.
J Chem Phys. 2023 Jul 28;159(4). doi: 10.1063/5.0150280.
Atomic description of electrochemical systems requires reactive interaction potential to explicitly describe the chemistry between atoms and molecules and the evolving charge distribution and polarization effects. Calculating Coulomb electrostatic interactions and polarization effects requires a better estimate of the partial charge distribution in molecular systems. However, models such as reactive force fields and charge equilibration (QEq) include Coulomb interactions up to a short-distance cutoff for better computational speeds. Ignoring long-distance electrostatic interaction affects the ability to describe electrochemistry in large systems. We studied the long-range Coulomb effects among charged particles and extended the QEq method to include long-range effects. By this extension, we anticipate a proper account of Coulomb interactions in reactive molecular dynamics simulations. We validate the approach by computing charges on a series of metal-organic frameworks and some simple systems. Results are compared to regular QEq and quantum mechanics calculations. The study shows slightly overestimated charge values in the regular QEq approach. Moreover, our method was combined with Ewald summation to compute forces and evaluate the long-range effects of simple capacitor configurations. There were noticeable differences between the calculated charges with/without long-range Coulomb interactions. The difference, which may have originated from the long-range influence on the capacitor ions, makes the Ewald method a better descriptor of Coulomb electrostatics for charged electrodes. The approach explored in this study enabled the atomic description of electrochemical systems with realistic electrolyte thickness while accounting for the electrostatic effects of charged electrodes throughout the dielectric layer in devices like batteries and emerging solid-state memory.
电化学系统的原子描述需要反应性相互作用势来明确描述原子与分子之间的化学作用以及不断演变的电荷分布和极化效应。计算库仑静电相互作用和极化效应需要对分子系统中的部分电荷分布有更好的估计。然而，诸如反应力场和电荷平衡（QEq）等模型为了获得更好的计算速度，将库仑相互作用计算到短距离截止。忽略长程静电相互作用会影响描述大型系统中电化学的能力。我们研究了带电粒子之间的长程库仑效应，并扩展了QEq方法以纳入长程效应。通过这种扩展，我们期望在反应性分子动力学模拟中能恰当地考虑库仑相互作用。我们通过计算一系列金属有机框架和一些简单系统上的电荷来验证该方法。将结果与常规QEq和量子力学计算进行比较。研究表明常规QEq方法中的电荷值略有高估。此外，我们的方法与埃瓦尔德求和相结合来计算力并评估简单电容器配置的长程效应。有无长程库仑相互作用时计算出的电荷之间存在明显差异。这种差异可能源于对电容器离子的长程影响，这使得埃瓦尔德方法成为带电电极库仑静电学的更好描述方法。本研究中探索的方法能够在考虑电池和新兴固态存储器等器件中整个介电层带电电极的静电效应的同时，对具有实际电解质厚度的电化学系统进行原子描述。
