A Graph-based Methodology for Modeling the Nucleation of Weak Electrolytes

在化学系化学理论、模型和计算方法项目的支持下，威斯康星大学麦迪逊分校的Jordan R. Schmidt教授将开发新的方法来模拟溶液中晶体的生长。晶体的成核和生长是一种普遍存在的现象，是许多化学和生物过程的基础，从水冰的形成到通过生物矿化的骨骼生长。施密特和他的研究团队将开发和应用新的方法，通过计算机模拟来检查晶体生长的初始阶段的原子细节，这可能为更好地理解如何指导和控制重要晶体材料的生长打开大门。特别强调的是对低溶解度的重要溶质的生长进行建模，例如，新兴的纳米多孔材料，现有的模拟方法是不够的。施密特教授还将通过参与威斯康星大学麦迪逊分校化学机会项目（ChOPS）和美国化学学会通往博士学位项目的桥梁项目，进一步努力拓宽理论化学的参与范围，包括本项目和更广泛的科学界。施密特团队还将把重点放在K-12的推广活动上，包括在当地小学和中学以及威斯康星科学节举行的晶体成核等现场化学演示。在这个项目中，威斯康星大学麦迪逊分校的施密特小组将开发并应用一种基于图论的方法，这种方法是针对晶体结构表现出定向键的材料量身定制的，无论是纯静电的，还是通过配位络合物，因此可以被描述为连接单体的“图”。使用自举方法，生长原子核的自由能将通过植根于统计热力学的严格方法来计算。该方法消除了这种弱电解质成核所固有的长度和时间尺度限制（例如质量输运、脱溶），这些限制目前阻碍了弱电解质成核的原子模拟。在开发、验证和优化以进一步提高这种基于图的方法的效率之后，该团队将探索在简单盐、弱电解质和纳米多孔材料（即金属有机框架）上的应用，这是一类重要的低溶解度材料，其中成核在材料合成和晶体工程中起着关键（通常是限制）的作用。生成的代码/脚本将通过GitHub以开源形式发布，以使整个科学界的应用程序能够应用于其他领域。该奖项反映了美国国家科学基金会的法定使命，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。

With support from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Professor Jordan R. Schmidt of University of Wisconsin-Madison will develop new methods for simulating the growth of crystals in solution. The nucleation and growth of crystals is a ubiquitous phenomenon that underlies many chemical and biological processes, from the formation of water ice to the growth of bone via biomineralization. Schmidt and his research team will develop and apply new methods that allow the initial stages of crystal growth to be examined in atomistic detail via computer simulations, potentially opening the door to a better understanding for how to direct and control the growth of important crystalline materials. A special emphasis will be placed on modeling the growth of important solutes with low solubility, e.g., emerging nano-porous materials, where existing simulation methods are inadequate. Professor Schmidt will also conduct additional efforts to broaden participation in theoretical chemistry, both in this project and in the wider scientific community, via participation in the UW Madison Chemistry Opportunities (ChOPS) and ACS Bridge to the Doctorate programs. The Schmidt team will also focus on K-12 outreach activities, including live chemistry demonstrations, including those on crystal nucleation, at local elementary and middle schools and the Wisconsin Science Festival.In this project, the Schmidt group at U. Wisconsin-Madison will develop and apply a graph theory-based methodology that is tailored toward materials whose crystal structure exhibits directional bonding, whether purely electrostatic, or via coordination complexes, and thus can be described as a “graph” of connected monomers. Using a bootstrapping approach, the free energies of growing nuclei will be calculated via a rigorous approach rooted in statistical thermodynamics. The methodology eliminates the length- and timescale limitations inherent to the nucleation of such weak electrolytes (e.g. mass transport, desolvation) that currently preclude the atomistic simulation of weak electrolyte nucleation. Following development, validation and optimizations to further enhance the efficiency of this graph-based approach, the team will explore applications to simple salts, weak electrolytes, and nano-porous materials (i.e., metal-organic frameworks), an important class of low-solubility material where nucleation plays a key (and often limiting) role in materials synthesis and crystal engineering. The resulting codes/scripts will be released in open-source form via GitHub to enable applications to other domains by the scientific community at large.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.