Archiv 2018

Vortragender: Yong-Jae Kim

Study of pressure-induced abnormal ice growth and multipath water-ice transition with dynamic diamond anvil cell

MPSD Seminar
Water, due to its unique hydrogen bonds, is one of the materials exhibiting diverse phases, crystal morphologies, and phase transformation. As a result of interplay between environmental conditions and molecular kinetics, more than 25 crystalline and amorphous ices have been reported with various growing morphologies from polyhedron to needle. Dynamic diamond anvil cell (dDAC), which may simply resolve the interference of macroscopic driving force and microscopic kinetics by changing compression rate, is essential to study complex phase transition behaviour of water. In the present study, we haveinvestigated the effect of compression rate on crystal growth and the multiple freezing-melting pathways of H2O under far-from-equilibrium condition by using dDAC at room temperature. First, we reveal the origin of shock growth of ice VI single crystal. Under rapid compression (strain rate > ~0.1 /s), we observed a morphological transition in ice VI growth from three-dimension (3-d) to twodimension (2-d) with one-order higher growth speed. It is found that local growth condition and interface kinetics can be affected by compression rate, which facilitate the 2-d shock growth. Secondly, we explore five different pathways of freezing and melting of deeply supercompressed water and ice via metastable phases. We will discuss the mechanism of freezing and melting by calculating driving force and interfacial free energy based on the classical nucleation theory, and comparing structure of supercompressed water and stable and metastable ices obtained from Raman spectroscopy. [mehr]
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