EAGER: Exploring the Application of Transition Zone Theory to Crystallization from Solutions

第一部分：结晶是人类研究的最早的化学过程之一，如史前时期从海水中结晶盐的实践证据所示。 如今，控制晶体生长的能力对于太阳能电池和激光器等技术设备以及药物制剂的制备至关重要。 然而，晶体生长的基本机制尚未完全理解。 经典的成核理论是被广泛接受的晶体生长模型，但它并不能完全解释实验测量结果。 在该项目中，由材料研究部内的固态和材料化学计划支持，PI将继续开发在他的实验室中开始的晶体生长的新模型，用于从熔融材料形成晶体。 新项目通过研究溶液中起始材料的排列以及固体晶体在不同条件下形成的速度，将这一理论扩展到溶液中的晶体生长。 总之，这些实验将增加对晶体生长的理解，最终使科学家能够开发出更好的程序来生长高质量的晶体。 该项目还包括培训学生和博士后研究人员，包括让他们参加国家同步加速器设施的先进实验。 第二部分：技术概述最近发展的结晶过渡区理论，基于结晶单元的协同性而不是经典的颗粒附着/分离概念，精确地描述了不同材料熔体的晶体生长速率。 该项目由材料研究部内的固态和材料化学计划支持，测试了类似的熵和合作影响负责控制溶液结晶的假设。 本工作通过研究二元相图系统中晶体生长的动力学来确定在晶体中形成长程有序和从结晶溶质中排除溶剂所需的相应活化能，从而将模型扩展到包括从溶液中结晶。该项目使用光谱和衍射方法来研究1）饱和溶液的结构，2）从纯相到低共熔组合物作为溶剂/溶质浓度的函数的比较结晶速率，和3）从不同溶剂中结晶的比较速率，其中强溶剂-溶质相互作用可能抑制结晶。 长期目标是过渡区理论模型的扩展可以为从纯金属到饱和溶液的连续体系中晶体生长的全面机理理解提供基础。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而被认为值得支持。

Part I: Non-Technical SummaryCrystallization was one of the earliest chemical processes studied by humans, as indicated by evidence of the practice of salt crystallization from seawater in pre-historic times. Today, the ability to control crystal growth is essential to technological devices such as solar cells and lasers as well as in preparation of pharmaceutical agents. However, the fundamental mechanisms underlying crystal growth are not fully understood. Classical nucleation theory, which is the widely accepted model for how crystals grow, does not fully account for experimental measurements. In this project, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, the PI will continue to develop a new model of crystal growth initiated in his laboratory for formation of crystals from molten materials. The new project extends this theory to crystal growth from solutions by studying the arrangement of starting materials in the solutions and the speeds at which solid crystals form under varying conditions. Taken together, these experiments will increase understanding of crystal growth, eventually allowing scientists to develop better procedures for growing high-quality crystals for applications. The project also encompasses training of students and postdoctoral researchers, including their participation in advanced experiments at national synchrotron facilities. Part II: Technical SummaryThe recently developed Transition Zone Theory of crystallization, based on the cooperativity of crystallizing units rather than a classical particle attachment/detachment conception, accurately describes the crystal growth rates from melts of diverse materials. This project, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, tests the hypothesis that similar entropic and cooperative influences are responsible for controlling crystallization from solution. This work extends the model to encompass crystallization from solution by studying the kinetics of crystal growth across binary phase diagram systems to determine the respective activation energy requirements to form long-range order in crystals and to exclude solvent from the crystallizing solute.Using representative systems of hydrated metal salts and aromatic organic molecules, the project uses spectroscopic and diffraction methods to investigate 1) the structure of saturated solutions, 2) comparative crystallization rates as a function of solvent/solute concentration from the pure phase to eutectic compositions, and 3) comparative rates of crystallization out of diverse solvents for which strong solvent-solute interactions are likely to inhibit crystallization. The long-term goal is that an extension of the Transition Zone Theory model can provide the basis for a comprehensive mechanistic understanding of crystal growth across a continuum of systems from pure metals to saturated solutions.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.