(443c) Crystal Nucleation and Growth in Molecular Systems

Controlling the crystallization of molecules from supersaturated solutions is a long-standing issue in solid state chemistry. Since polymorphs may have very different physical properties, it is crucial to control in which polymorph a molecule crystallizes in many applications, such as e.g. in the pharmaceutical industry. We discuss in this presentation our recent work on the molecular simulation of the crystallization of molecules from the liquid phase. We simulate the nucleation step using a combination of molecular dynamics simulation with the so-called umbrella sampling technique. This sampling method, when used together a reaction coordinate (or order parameter) characteristic of the crystalline order for the chosen system, is particularly well suited to study activated processes (or rare events) such as e.g. the nucleation event, which requires the system to overcome a large free energy barrier of nucleation. Throughout the nucleation and growth processes, we focus on examining how the selection of a specific polymorph takes place.