Simulation and Theory of Crystal-Melt Interfaces

Brian Laird博士得到了理论和计算化学计划的资助，继续他对晶体-熔体界面的模拟和理论的研究。 Laird在这一领域的前期工作主要集中在理想化硬球系统的固液界面。 拟议的继续将这项工作扩展到更现实的系统，如金属和金属合金，并与取向依赖的相互作用的系统。 密度泛函理论结合形式统计力学将用于：1）计算界面自由能; 2）预测溶质在混合物（如金属合金）界面的偏析; 3）预测分子系统固液界面的结构和动力学。 由于这一研究领域的实验数据严重缺乏，模拟将提供“实验”数据，以评估和发展这类系统的分析理论。为了充分理解晶体生长、均匀成核、平衡晶体形状或平衡溶质偏析等重要的技术现象，有必要详细了解晶体与其熔体之间界面的微观特性。 不幸的是，几乎完全缺乏这种系统的实验数据，使这些研究变得困难。 因此，计算方法，如计算机模拟技术提出的莱尔德远远超出了他们通常的作用，在解释实验数据，并成为重要的数据，根据这些重要的过程分析理论。

Dr. Brian Laird is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research on the simulation and theory of crystal-melt interfaces. Laird's prior work in this area has been focused on the solid-liquid interface for idealized hard sphere systems. The proposed continuation will extend this work to more realistic systems such as metals and metal alloys and to systems with orientationally dependent interactions. Density-functional theory in conjunction with formal statistical mechanics will be used to: 1) calculate the interfacial free energy; 2) predict the solute segregation at the interface for mixtures such as metal alloys; and 3) predict the structure and dynamics for solid-liquid interfaces of molecular systems. Since there is a significant lack of experimental data in this area of research, the simulations will provide "experimental" data with which to evaluate and develop analytical theories for such systems.In order to fully understand such technologically important phenomena as crystal growth, homogeneous nucleation, equilibrium crystal shapes or equilibrium solute segregation, it is necessary to have detailed information on the microscopic properties of the interface between a crystal an its melt. Unfortunately, there is nearly a total lack of experimental data on such systems making these studies difficult. Thus, computational methods such as the computer simulation techniques proposed by Laird go far beyond their usual roles in the interpretation of experimental data and become important data upon which to base analytical theories for these important processes.