主 讲 人:Peter G. Kusalik 教授
Peter G. Kusalik 教授，加拿大卡尔加里大学理学院的规划和运营院长。研究兴趣为利用分子模拟来提供对微观尺度的液体、溶液和固体行为的见解。他的研究为结晶等过程提供了许多新见解，在揭示潜在的集体分子机制、大气科学、材料科学、分子生物学和食品科学等领域产生潜在的巨大影响。他在Science、PNAS、JACS、Phys. Rev. Lett.等著名期刊上发表了多篇论文，目前的总引用次数超过6180次，平均引用率为55。并担任Science和Nature等知名期刊审稿人。
Crystallization is relevant to many disciplines, and its control (i.e. promotion or inhibition) is of great importance across a wide range of technological applications, including gas hydrates. Gas clathrate hydrates, ice-like solids in which gas molecules such as methane are trap in water cages, have considerable scientific and industrial importance. For example, the formation of gas hydrates in oil and gas pipelines is an ongoing problem. Yet, the molecular-level mechanisms responsible for the initial formation of gas hydrates (i.e. their nucleation) have proven difficult to study directly with experiments, in part due to the stochastic nature of the underlying molecular behaviours. Molecular dynamics simulations have recently been demonstrated to be able to provide many molecular-level insights, since they are able to probe directly the microscopic environment during the nucleation and growth of a crystal. Additionally, most theoretical treatments of nucleation, and of gas hydrate as a particular example, rely on approaches originating from classical nucleation theory (CNT), yet key assumptions upon which CNT is based have been brought into question by a number of recent studies. In this presentation I will begin with a brief review of the key issues around simulations of crystallization, considering some of the attributes and limitation of various models and methods. Specific results for gas hydrates, as well as for ice, will be used illustratively to demonstrate that the process of crystallization is characterized by collective phenomena involving many molecules, where the organization can be seen to occur in stages. The nature of the structural fluctuations that characterize these ordering processes, including their impact upon the evolution of nascent crystallites on a nanosecond timescale, will be examined. The important roles played by defect structures in the observed behaviours will be highlighted, and I will consider how structure fluctuations can couple to local perturbations (e.g. confining surfaces). I will also show how rugged funnel-shaped potential energy landscapes, a representation used widely to help describe protein folding, provide a general approach for understanding the phenomenology of crystal nucleation in gas hydrates. These insights provide opportunities for a new framework for understanding the structural evolution during nucleation, and suggest a first-principles approach for generating kinetic models of nucleation that remain faithful to underlying molecular details.