Molecular-dynamics simulations of urea nucleation from aqueous solution

Significance Nucleation from solution is a ubiquitous process that plays important roles in physics, chemistry, engineering, and material science. Despite its importance, nucleation is far from being completely understood. In this work, we combine advanced molecular-dynamics simulation techniques and theory to provide a description of urea nucleation from aqueous solution. In particular, our analysis shows that a two-step nucleation mechanism is favorable and that two polymorphs are seen to compete in the early stages of the nucleation process. In our analysis, we have derived and validated a theoretical correction to finite-size effects to compute free-energy profiles in the limit of a macroscopic system at constant supersaturation.