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IGM Colloquium: Geometrically frustrated assemblies

© 2018 EPFL / Prof. Efi Efrati

© 2018 EPFL / Prof. Efi Efrati

Geometrically frustrated assemblies
Unlike Lego bricks that perfectly assemble next to one another, in molecular assemblies some misfit is almost always present.

The molecular constituents thus must distort in order to form an aggregate, resulting in a frustrated assembly. The generation of geometric frustration from the intrinsic geometry of the constituents of a material is not only natural and ubiquitous but also leads to a striking variety of morphologies of ground states and exotic response properties.
In this talk, I will review the notion of cumulative geometric frustration and discuss two distinct examples of geometrically frustrated assemblies: liquid crystals in 2D, and twisted molecular crystals that form banded spherulites. For liquid crystal, we will present how to quantify the frustration and give specific examples that exhibit super-extensive elastic energy. Motivated by the twisted crystals observed for a wide variety of organic molecular crystals studied by the Kahr group in NYU, we study a model of frustrated assembly that in particular conveys the nano-metric pitch length of the constituents to the tens of microns pitch length observed for the twisted crystalline assemblies.

I graduated in 2010 from the Hebrew university of Jerusalem where I did my Ph.D. under the guidance of Eran Sharon and Raz Kupferman studying frustrated elastic structures. I then moved to the James Franck Institute at the University of Chicago where I was a Simons Postdoctoral fellow. Since 2014 I have been an assistant professor in the department of Physics of complex systems at the Weizmann institute of Science.