J. Tao
Pacific Northwest National Laboratory,
United States
Keywords: AFM, thermodynamics, kinetics, crystallization
Summary:
The mechanism of the interplay between additives and crystals is a long-term mystery in the field of crystallization. Monitoring crystallization processes in real time is challenging due to the sub-nanometer scale and highly dynamic nature of the incorporation/detachment events. As a result, to date material synthesis has been advanced mainly by empirical optimization of different synthesis parameters (concentration, temperature or solvent) rather than by rational manipulation based on thermodynamic or kinetic controls. As a result, there is a significant knowledge gap in understanding 1) how additive interact with growth units resulting in changes in the thermodynamics and kinetics of crystallization, and 2) how additives affect elementary processes such as transport, adsorption, and desolvation of growth unit at interface. From the energetic viewpoint, incorporation of growth units at the additive-crystal interfaces depends on the balance between the kinetic factor—the desolvation or reorganization energy at interfaces—and the thermodynamic factor—the structural changes created by incorporation on the crystal surfaces. Combining in situ high resolution atomic force microscopy (AFM), spectroscopies and ab initio molecular dynamics computational simulations, we have quantified the effect of additives on the solubility, kinetic coefficient, prefactor and interfacial energy for crystallization by tuning desolvation energies and/or relaxing structural features of growth units via a specific configuration at the growth front. This general mechanism has been evaluated in diverse crystal systems including biomaterials, heterostructural materials, and energy materials. Understanding the kinetics and energetics of additive-controlled nucleation, crystal growth and dissolution will underlie the development of predictive synthesis methodologies for functional materials with tunable properties.