Research

 

Interfacial Structure of Crystals and Kinetics of Crystallization

• The surface roughening transition and the structure of crystal-liquid interfaces;

• The prediction of the morphology of crystals, and crystal habit modifiers and/or crystallization inhibitors design by surface recognition;

• The mechanisms of nucleation and crystals growth;

• Spherulitic crystallization and crystal network (aggregation) formation;

• Microemulsion crystallization and nanomaterials preparation;

• Biocrystallisation;

• Protein crystallization;

• Template and nanoparticle engineering.

The kinetics of crystallization and the morphology of crystals is determined by the structure of crystal/fluid interfaces.  Conventionally, only the effect of crystal structure is taken into account.  This leads to the inaccurate prediction and description of crystallization behavior.  Our new development allows to predict precisely the genuine morphology of crystals, and the effect of the fluid phase (including additives, solvents etc.) on growth habits, based on MD simulations and an analysis of crystal/fluid interfacial structure and interfacial kinetics processes. Based on the results, the molecular  design of polymeric additives becomes possible from an interfacial structural analysis.  This work provides new opportunities for the rational design of additives for the control of crystal habit and crystallization. (c) Snapshot of MD simulation for the interface between crystalline Urea (left) and saturated aqueous solution (right)  in the {001} orientations.

 

 

The work allows a quantitative description of the effect of foreign bodies on the growth of crystals by our new kinetic model.  According to our prediction, foreign particles adsorbed at a growing crystal surface will promote the growth of the surface due to the lowering of 2D nucleation barrier.  In the case where foreign particles lead to the formation of 2D nucleation potential well at the crystal surface, a so-called particle-induced surface instability will occur. (a) and (b) Illustration of 2D nucleation barrier well caused by a foreign particle and the corresponding growth pattern of surface instability. (c)  The occurrence of particle-induced surface instability at the {110} faces of naphthalene

 

 

A new and generic model has been developed to describe the effect of foreign bodies on the kinetics of nucleation related processes.  Some very important and new phenomena have been identified for the first time from our research:

•High supersaturation driven structural mismatch between nucleating phase and substrate;

•Zero size effect;

• Non-classical epitaxial effect;

• Molecular templating effect.

These developments exert significant impact on micro/nano structural fabrication and engineering; epitaxial growth, bio mineralization and engineering, etc.