Collaborative Research: Fluid Polyamorphism: Theory, Experiment and Simulation

该项目由化学部化学结构、动力学和机理-A(CSDM-A)计划资助，支持马里兰大学学院公园分校、亚利桑那州立大学、波士顿大学和普林斯顿大学的科学家和工程师之间的合作。合作小组使用理论、计算和实验方法来研究液体中可能出现的不同类型的分子结构。液体中的分子虽然不像固体晶体中那样有序性，但仍可能形成可区分的结构类型。这种现象被称为多晶化，据预测，这种现象会在冰点以下和高压的水中发生。该团队正在使用实验技术，如量热法(测量当样品经历相变时流入和流出的热量)、红外光谱(以表征系统中的分子振动)和计算工具(分子动力学模拟)来表征水和其他液体中的多晶相。除了获得对物质本质的基本见解外，这项调查的结果可能会对玻璃技术、低温生物学和大气科学等领域产生影响。参与这个项目的研究生正在获得实验和计算化学方面的经验，他们受益于不同参与机构之间的人员交流。该项目的更广泛影响可能包括基于硅替代品的计算机硬件的开发、更好的药物配方、低温组织保存的新方法、高中生的计算模型，以及基于对云微物理的更好理解而进行的更准确的天气预报。该项目涉及开发和验证描述单组分物质多晶性的通用热力学方法。统一的概念是相互竞争的分子或超分子结构之间的平衡相互转化。模拟研究包括手性驱动、液-液相分离、深过冷条件下的临界行为和有限尺寸标度，以及结晶、流体相分离和流体结构松弛之间的相互作用。量热法、光学显微镜、动态光散射、红外和拉曼光谱以及透射电子显微镜为包括非晶化水溶液在内的多晶系提供了互补的实验表征。两态热力学形式主义提供了统一的理论观点。该项目的更广泛影响可能包括基于硅替代品的计算机硬件的开发、更好的药物配方、低温组织保存的新方法、高中生的计算模型，以及通过提高对云微物理的理解来更准确地预测天气。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project, funded by the Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) program of the Chemistry Division, supports a collaboration between scientists and engineers at the University of Maryland at College Park, Arizona State University, Boston University, and Princeton University. The collaborative team employs theoretical, computational, and experimental methods to investigate the different types of molecular structures that can occur in liquids. The molecules within a liquid, while not as ordered as they would be in a solid crystal, may still form distinguishable types of structures. This phenomenon, known as polyamorphism, has been predicted to occur in water at sub-freezing temperatures and high pressures. The team is employing experimental techniques such as calorimetry (to measure the flow of heat into and out of samples as they undergo phase changes), infrared spectroscopy (to characterize the molecular vibrations in the system), and computational tools (molecular dynamics simulations) to characterize polyamorphic phases in water and other liquids. In addition to gaining fundamental insights into the nature of matter, the results of this investigation may have impacts in fields such as glass technology, cryobiology, and atmospheric science. The graduate students involved in this project are gaining experience in both experimental and computational chemistry, They benefit from personnel exchanges among the different participating institutions. The broader impacts of the project may include development of computer hardware based on silicon alternatives, better pharmaceutical formulations, new routes to low-temperature tissue preservation, computational models for high school students, and more accurate weather predictions based on an improved understanding of cloud microphysics.This project involves the development and verification of a generic thermodynamic approach to describe polyamorphism in single-component substances. The unifying concept is that of equilibrium interconversion between competing molecular or supramolecular structures. Simulations involve studies of chirality-driven, liquid-liquid phase separations, critical behaviors and finite-size scaling under deeply supercooled conditions, and the interplay between crystallization, fluid phase separation, and fluid structural relaxation. Calorimetry, optical microscopy, dynamic light scattering, infrared and Raman spectroscopies, and transmission electron microscopy provide complementary experimental characterization on polyamorphic systems, including non-crystallizing aqueous solutions. The two-state thermodynamic formalism provides a unifying theoretical perspective. The broader impacts of the project may include development of computer hardware based on silicon alternatives, better pharmaceutical formulations, new routes to low-temperature tissue preservation, computational models for high school students, and more accurate weather prediction through improved understanding of cloud microphysics.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.