CAREER: Nucleation from solution: a new frontier for molecular simulation

加州大学圣巴巴拉分校的Baron Peters获得了化学系理论、模型和计算方法项目的职业奖，以开发分子模拟策略，了解溶液成核临界核的分子水平特性。成核是一个新相的第一个微观胚胎形成以引发相变的过程。了解影响成核速率的因素以及决定核是稳定还是不稳定的核的特征是实验和模拟的主要挑战。PI使用路径采样，原子模拟，晶格模型和粗粒动力学来了解纳米尺度下临界核结构和界面能量贡献的各个方面。这项工作扩展了球形粒子和隐式溶剂以外的成核模拟。这些努力结合了联合收割机的最先进的方法，罕见的事件与严格的方法来控制化学势（过饱和）在凝聚相。 核化的常见例子是在打开的苏打水中形成二氧化碳气泡，或者在放在冰箱里的一瓶水中形成冰晶。 实际上，这些可见的液滴、气泡或新相的晶体实际上是相变的后期阶段。只有几个分子的微观原子核可能会形成并重新溶解多次，然后最终产生一个稳定的原子核，最终可以生长到可见的大小。在某些情况下，比如冰箱里的瓶装水，在第一个稳定的核形成之前，可能需要几个小时或几个星期。 专门为溶液成核设计的新模拟方法提供了机械见解，以指导具有受控晶体结构，形状和性能的材料的结晶和合成。从这项工作中获得的见解促进了药物的制备，电子和催化材料的合成以及结晶纯化。

Baron Peters of the University of California, Santa Barbara is supported by a CAREER award from the Theory, Models and Computational Methods Program in the Chemistry Division to develop molecular simulation strategies for understanding molecular level properties of critical nuclei for nucleation from solution. Nucleation is the process by which the first microscopic embryo of a new phase is formed to initiate a phase transition. Understanding the factors that influence nucleation rates and the features of a nucleus that determine whether it is stable or unstable is a major challenge for experiments and for simulations. The PI uses path sampling, atomistic simulations, lattice models and coarse grained dynamics to understand various aspects of the critical nucleus structure and interfacial energy contributions at the nanoscale. This work extends simulations of nucleation beyond spherical particles and implicit solvents. These efforts combine state-of-the-art methods for rare events with rigorous methods to control the chemical potential (supersaturation) in the condensed phase. Familiar examples of nucleation are the formation of carbon dioxide bubbles in an opened soda or ice crystals in a bottle of water placed in the freezer. Actually these visible droplets, bubbles, or crystals of the new phase are actually later stages in the phase transformation. Microscopic nuclei with just a few molecules may form and re-dissolve many times before finally giving birth to a stable nucleus that can eventually grow to a visible size. In some cases, like the example of bottled water in the freezer, hours or weeks may pass before the first stable nucleus forms. New simulation methods designed specifically for nucleation from solution provide mechanistic insights to guide the crystallization and synthesis of materials with controlled crystal structures, shapes, and properties. The insights gained from this work facilitate the preparation of pharmaceuticals, the synthesis of electronic and catalytic materials, and purification by crystallization..