Berlin 2024 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 45: Modeling and Simulation of Soft Matter IV
CPP 45.2: Vortrag
Donnerstag, 21. März 2024, 15:15–15:30, H 0111
Microscopic insights on the puzzling saddle-splay elasticity of nematics — •Davide Revignas1,2 and Alberta Ferrarini1 — 1Department of Chemical Sciences, Padua, Italy — 2Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
The elasticity of a nematic liquid crystal is commonly understood in terms of the Frank deformation free energy which involves splay (K11), twist (K22) and bend (K33) elastic constants. There exists, however, a fourth term commonly referred to as the saddle-splay deformation mode, which is associated to the elastic constant K24.
Recent experiments on confined chromonic liquid crystals revealed a twisted ground state which has been ascribed to K24 > K22. This would violate one of the Ericksen inequalities for the stability of the nematic uniform state. In general, experimental estimates of K24 are difficult to obtain and only few, sometimes contradictory data are available. Moreover, the estimation of K24 is a challenging task also for microscopic theories of elasticity; indeed, the very possibility of an unambiguous calculation of this quantity starting from a microscopic model has been questioned.
Here we will present the results of the calculation of the full set of elastic constants, including K24, for simple hard rods in the framework of Onsager theory for nematics. Such results enable us to discuss the possible origin of a twisted ground state for this simple model of nematics, in spite of the absence of microscopic chirality.
Keywords: nematics; elasticity; saddle-splay