The Dynamics of Phase Changes in Molecular Clusters

在化学学部实验物理化学计划的这个项目中，Bartell将研究相变中均匀成核的动力学，他将使用两种与研究固态转变相关的新技术。在实验上，他将利用电子衍射在不同的飞行时间探测在超音速流动中产生的团簇，以监测分子“相变”期间填料的变化。他还将使用分子动力学模拟来描述分子行为的计算特征。模拟将揭示“临界核”的形成过程。许多相同的相变将使用这两种技术来研究。研究成核，例如固态或液态物质从一相到另一相的变化，在许多科学和技术领域具有至关重要的意义，如气象学、材料工程、石油催化和地球科学。这项研究计划旨在通过检查分子排列的不同方式，更好地了解这种均匀的相变。本程序特别强调的是相变速率的理论预测和实验测量的比较。将对成核理论进行新的测试，从而深入了解相变的分子机制。

In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Bartell will study the dynamics of homogeneous nucleation in phase changes in which he will use two new techniques which are relevant to studying solid-state transformations. Experimentally he will probe clusters generated in a supersonic flow using electron diffraction at various times-of-flight to monitor changes in packing during molecular "phase transitions." He will also characterize the molecular behavior computationally using molecular dynamics simulations. The formation of "critical nuclei" will be revealed by the simulations. Many of the same phase transitions will be studied using both techniques. %%% Studies of nucleation, such as the changes from one phase to another in solid- or liquid-state matter, are of crucial importance in many areas of science and technology, such as meteorology, materials engineering, petroleum catalysis, and earth sciences. This research program aims at acquiring a better understanding of such homogeneous phase changes by examining the different ways that molecules are packed in arrays. A special emphasis of this program is a comparison of theoretical prediction and experimental measurement of the rate of phase transitions. New tests of nucleation theory will be made, resulting in insights into the molecular mechanisms of phase changes.