Collaborative Research: Fluid Polyamorphism: Theory, Experiment, and Simulation

点击翻译按钮获取中文摘要

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.