RUI: Mesoscale Methods for Electrochemistry: Confronting the Complexity of Ion and Electron Transfer

维拉诺瓦大学的Ryan Jorn教授获得了化学系化学理论，模型和计算方法项目的奖项。 Jorn教授开发了研究电极表面电子和离子传输的方法，特别关注可充电电池中存在的反应界面。 虽然可充电电池对于为个人电子产品提供动力至关重要，但它们也可能通过为汽车提供动力而在减少碳排放方面发挥重要作用。 用于运输的能源储存仍然存在一些技术挑战，包括随着时间的推移储存容量的损失和充电率低。 这些挑战与离子和电子在分子水平上的传输密切相关。 不幸的是，电荷传输机制知之甚少。 很少有实验能够在电极表面获得足够小的长度和时间尺度。 大多数计算机模拟也不足以描述电池运行期间工作的多个长度尺度。 研究电子的行为需要使用量子力学来正确处理它们的波动性质。 然而，这样的计算只适用于相对少量的原子。 准确地捕捉电子穿过的界面的演化需要在很长一段时间内考虑数千个原子。 Jorn教授的研究使用多尺度方法来研究这些问题。 他和他的同事计算 量子力学中的分子力 然后，他们使用这些力来描述电极表面的离子和分子的经典运动。 他在维拉诺瓦大学的工作在很大程度上依赖于本科生的参与，他们接受了最先进的仿真软件和高性能计算平台的培训。 Jorn教授还利用他的研究，通过维拉诺瓦大学的访问，成功和进步中心向第一代和代表性不足的大学生介绍计算建模。电化学界面的分子模拟以前依赖于从头算分子动力学（AIMD）来研究化学反应，以及经典分子动力学（CMD）来探索溶剂化现象。 关于前者，模拟的时间尺度上的限制，使运输现象的描述棘手。 另一方面，人们普遍认为，CMD中使用的“现成”力场无法准确捕获极化效应和界面结构。Jorn教授的研究通过采用一种力匹配方法来解决这些缺陷，该方法使用量子AIMD模拟的信息来训练经典分子力场。 他的研究小组通过探索分子间相互作用的不同功能形式和采样高能配置，探索如何最好地在界面上建立力场。 除了开发界面过程的力场外，Jorn教授的工作还包括开发增强的采样方法来描述电解质/电极界面上的物种交换。 通过使用一个独特的副本交换伞采样和集体变量的组合，他的方法允许研究单个缺陷迁移以及相关的机制，涉及离子“敲除”。 关于电子的运动，Jorn教授的工作采用Newns-Anderson Hamiltonian结合系综散射理论来描述还原过程中分子上的经典力。 Jorn教授在经典模拟中加入了电子转移，正在开发一个在分子水平上研究电化学的框架。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Project AbstractProfessor Ryan Jorn of Villanova University is supported by an award from the Chemical Theory, Models, and Computational Methods program in the Division of Chemistry. Professor Jorn develops methods to study the transport of electrons and ions at electrode surfaces, with particular focus on the reactive interfaces present in rechargeable batteries. While rechargeable batteries are essential to powering personal electronics, they may also play a significant role in reducing carbon emissions by powering cars. Several technical challenges to energy storage for transportation remain, including loss of storage capacity over time and poor rates of recharge. These challenges are intimately connected to the transport of ions and electrons at the molecular level. Unfortunately, charge transport mechanisms are poorly understood. Few experiments can access sufficiently small length and time scales at the electrode surface. Most computer simulations are also inadequate to describe the multiple length scales at work during battery operation. Studying the behavior of electrons requires using quantum mechanics to properly treat their wave-like nature. Such calculations, however, are only feasible for a relatively small numbers of atoms. Accurately capturing the evolution of the interface through which the electron travels requires accounting for thousands of atoms for very long times. Professor Jorn's research uses a multi-scale approach to study these problems. He and his coworkers compute molecular forces from quantum mechanics. They then use these forces to describe the classical motion of ions and molecules at the electrode surface. His work at Villanova University relies heavily on the involvement of undergraduate students who are trained on state-of-the-art simulation software and high-performance computing platforms. Professor Jorn also uses his research to introduce first generation and under-represented college students to computational modeling through the Center for Access, Success, and Advancement at Villanova University. Molecular simulations of electrochemical interfaces have previously relied on ab initio molecular dynamics (AIMD) to study chemical reactions, and classical molecular dynamics (CMD) to explore solvation phenomena. Regarding the former, limitations on the time scales of simulation render description of transport phenomena intractable. On the other hand, it is widely recognized that "off-the-shelf" force fields used in CMD fail to accurately capture polarization effects and interface structure. Professor Jorn's research addresses these deficiencies by employing a force-matching approach that uses information from quantum AIMD simulations to train classical molecular force fields. His research group explores how best to build force fields at interfaces by exploring different functional forms for intermolecular interactions and sampling high-energy configurations. In addition to developing force fields for interfacial processes, Professor Jorn's work includes developing enhanced sampling methods to describe the exchange of species across the electrolyte/electrode interface. By using a unique combination of replica exchange umbrella sampling and collective variables, his approach allows for the study of single defect migration as well as correlated mechanisms involving ion "knock-off". Regarding the motion of electrons, Professor Jorn's work employs a Newns-Anderson Hamiltonian coupled with ensemble scattering theory to describe the classical force on molecules during reduction. In adding electron transfer to classical simulations, Professor Jorn is developing a framework to study electrochemistry at a molecular level.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.