| 报告题目 | Non Classical Nucleation and Crystallization |
| 报告人 | Prof. Dr. Helmut Cölfen |
| 报告人单位 | Department of Physical Chemistry, Universität Konstanz, Germany |
| 报告时间 | 2014-09-01 |
| 报告地点 | 合肥微尺度物质科学国家实验室一楼科技展厅 |
| 主办单位 | 合肥微尺度物质科学国家实验室、中国科学技术大学化学与材料科学学院 |
| 报告介绍 | 报告摘要：
The description of nucleation has been dominated by the classical nucleation theory (CNT) for more than 80 years. However, significant problems exist for the understanding and description of real nucleation or crystallization events using CNT. Most problematic in CNT is certainly the assumption of bulk properties even for the smallest metastable clusters. Instead, it has turned out for CaCO3 and several other systems that nucleation can also follow an alternative pathway involving prenucleation clusters, which are thermodynamically stable with respect to the initial ions and are solutes containing some tens of ions. It turned out that for CaCO3, the prenucleation clusters can be understood as dynamic polymers and their formation is entropically driven by release of ion hydration water. Prenucleation clusters even form in undersaturated solution without driving force towards precipitation. The current knowledge about prenucleation clusters will be presented and discussed.
However, even beyond the stage of nucleation, crystal growth does not necessarily proceed along the classical mechanism of the addition of atom/ion/molecule building units to the growth sites of a growing crystal. Instead, nanocrystals can self assemble via different mechanisms or crystallize from an amorphous precursor phase to form so called "Mesocrystals". This is an abbreviation for "Mesoscopically structured crystals" and involves the crystallographically aligned superstructure of nanoparticles as a kinetic intermediate. Potential fusion of the already crystallographically aligned nanoparticles after displacement of surface attached stabilizer molecules can lead to crystallographic fusion of the two aligned crystal faces better known as "Oriented Attachment". These processes are known as "Nonclassical Crystallization". Several of these nonclassical mechanisms will be presented and discussed.
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