Experimental Studies of the Liquid-Glass Transition

9980370 cummins这个项目用激光散射光谱研究了液体-玻璃转变附近的液体和固体玻璃的动力学。最近的理论和实验研究表明，过冷液体中的放松（或记忆）功能表现出长达数十年的复杂行为。目前的研究方向是测量这些功能及其随温度降低的变化。数据分析将利用模式耦合理论（MCT）的扩展，现在包括方向自由度。系统地研究分子玻璃原盐中的极化和去极化布里渊散射，以探索用这种技术可以可靠地确定弛豫函数的程度。它们将用于评估这些结果与MCT的兼容性，MCT提供了密度相关函数及其随温度变化的详细预测。此外，玻璃在低温下的动力学，其中老化现象和双时间尺度行为已被理论预测和在计算机模拟中观察到。所开发的技术也将应用于包括弹性体在内的新材料，这些材料中的液体和玻璃相被中间弹性体（或橡胶）相分离。液体-玻璃转变是凝聚态物理中最古老的尚未解决的基本问题之一。它也是制造各种玻璃，包括塑料和玻璃金属合金的主要实际问题。将测试当前模式耦合理论，以评估松弛（或记忆）功能可以用这种技术可靠地确定的程度。此外，玻璃在低温下的动力学，其中老化现象和双时间尺度行为已被理论预测和在计算机模拟中观察到。所开发的技术也将应用于包括弹性体在内的新材料，这些材料中的液体和玻璃相被中间弹性体（或橡胶）相分离。该研究项目利用激光散射技术，将主要由研究生和博士后研究人员进行。该项目将包括与美国和欧洲其他研究小组的合作

9980370CumminsThis project investigates the dynamics of liquids in the vicinity of the liquid-glass transition and of solid glasses by laser light scattering spectroscopy. Recent theoretical and experimental research has shown that relaxation (or memory) functions in supercooled liquids exhibit complex behavior extending over many decades in frequency. Current research is directed at measuring these functions and their evolution with decreasing temperature. The data analysis will utilize an extension of mode coupling theory (MCT) that now includes orientational degrees of freedom. A systemic investigation of both polarized and depolarized Brillouin scattering in the molecular glass-former salol will be carried out to explore the extent to which relaxation functions can be determined reliably with this technique. They will be used to assess the compatibility of such results with MCT, which provides detailed predictions for density correlation functions and their evolution with temperature. In addition, the dynamics of glasses at lower temperatures where aging phenomena and two-time scaling behavior has been predicted theoretically and observed in computer simulations will be pursued. The techniques developed will also be applied to new materials including elastomers, materials in which the liquid and glass phases are separated by an intermediate elastomer (or rubber) phase.%%%The liquid-glass transition is one of the oldest unresolved fundamental problems in condensed matter physics. It is also of major practical concern in the manufacture of various glasses including plastics and glassy metallic alloys. Current mode coupling theories will be tested to assess the extent to which relaxation (or memory) functions can be determined reliably with this technique. In addition, the dynamics of glasses at lower temperatures where aging phenomena and two-time scaling behavior has been predicted theoretically and observed in computer simulations will be pursued. The techniques developed will also be applied to new materials including elastomers, materials in which the liquid and glass phases are separated by an intermediate elastomer (or rubber) phase.This research project utilizes laser light-scattering techniques and will be conducted by primarily by graduate students and postdoctoral researchers. The program will include collaborations with other research groups both in the US and in Europe.***