Shedding light on phase transformations in amphidynamic crystals
Omer Yaffe a
a Weizmann Institute of Science, Herzl St. 234, Rehovot 7610001, Israel
Proceedings of Dynamic Materials, Crystals and Phenomena Conference (DynaMIC23)
Fribourg, Switzerland, 2023 March 22nd - 24th
Organizers: Jovana Milic and Simon Krause
Invited Speaker, Omer Yaffe, presentation 027
Publication date: 15th February 2023

My group uses Raman spectroscopy to study the interaction between intermolecular vibrational modes in crystals.
Interactions between thermally activated vibrational modes (i.e., anharmonic interactions) cause thermal expansion, heat transport, and phase transformations.
Phase transformations in amphidynamic crystals are fascinating because they involve both the rigid scaffolds' small-amplitude vibrations and the mobile elements' large-amplitude motion. 

In my talk, I will present a study where we identify the vibrational modes associated with the phase transition by following the position and width of the Raman peaks with temperature. 
We compare two amphidynamic crystals that show distinct behavior.
In one crystal, strong damping of a single vibrational mode is responsible for the phase transition and the 'unlocking' of large amplitude motion of the mobile element in the crystal. 
Therefore, its behavior follows an analytical model that offers predictive power.   
In the second crystal, a few lattice modes are simultaneously involved in the phase transition leading to much more complex behavior. 
Our study offers insight into the design of tailor-made amphidynamic crystals.   

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