Dynamics of First-Order Phase Transitions

David Oxtoby得到了理论和计算化学计划的资助，继续他在成核理论方面的工作。他将使用统计力学技术，主要是密度泛函方法，来研究一级相变的动力学。这种转变在许多科学和技术领域都具有核心重要性。当前研究计划的目标是开发新的理论方法，以能够预测气-液和液-固相变的成核率。Oxtoby使用的密度泛函方法在一定程度上结合了原子水平的相互作用，这在传统的经典成核理论中是不可能的。未来三年研究计划的具体目标包括：1)更好地了解偶极相互作用对成核的影响；2)产生微乳液的水-油-表面活性剂三组分体系相图的微观和预测性方法；3)改进的金属合金晶体成核理论；4)蛋白质结晶及其与凝聚的关系的新方法；以及5)仔细研究固体基质和电场对晶体成核的影响。成核在许多科学和技术领域都很重要，包括：1)云中水蒸气的凝结和冻结；2)从熔体中浇铸固体金属和金属合金；以及3)从溶液中生长蛋白质晶体，以确定其结构。在分子水平上，这些状态变化的机制还没有被很好地理解，也许最不被理解的方面是新相的第一个团簇出现的速度。这一步骤被定义为成核，通常是新相形成的速率决定因素，这也是Oxtoby的研究试图阐明的步骤。

David Oxtoby is supported by a grant from the Theoretical and Computational Chemistry Program to continue his work on nucleation theory. He will use statistical mechanical techniques, primarily density functional approaches, to investigate the dynamics of first-order phase transitions. Such transitions are of central importance in many areas of science and technology. The objective of the current research program is to develop new theoretical approaches to be able to predict nucleation rates for gas-liquid and liquid-solid phase transitions. The density functional approach used by Oxtoby incorporates atomic-level interactions to an extent not possible in traditional classical theories of nucleation. Specific targets of the research program for the next three years include: 1) a better understanding of the effects of dipolar interactions on nucleation; 2) a microscopic and predictive approach to the phase diagrams of three-component water-oil-surfactant systems that produce microemulsions; 3) an improved theory of crystal nucleation in metal alloys; 4) a new approach to protein crystallization and its relation to coagulation; and 5) a careful study of the effects of solid substrates and electric fields on crystal nucleation. Nucleation is important in a number of areas of science and technology including: 1) the condensation and freezing of water vapor in clouds; 2) the casting of solid metals and metal alloys from the melt; and 3) the growth of protein crystals from solution in order to determine their structure. On a molecular level, the mechanism of these changes of state are not well understood, and perhaps the least-understood aspect is the rate at which the first clusters of the new phase appear. This step, defined as nucleation, is often rate-determining for the formation of the new phase, and it is the step which Oxtoby's research will attempt to elucidate.