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Abstract: A theoretical study of the variation of thermodynamic and transportproperties of calamitic liquid crystals across the isotropic-nematic phasetransition is carried out by calculating the {\it wavenumber k and time t}dependent intermediate scattering function of the liquid, via computersimulations of model nematogens. The objective is to understand theexperimentally observed anomalies and sharp variation in many thermodynamic andtransport properties, namely specific heat $C$, sound attenuation coefficient$\Gamma$, thermal diffusivity $D T$ and sound velocity $c s$ are as the I-Ntransition is approached from the isotropic side. The small wavelength limit ofthe calculated intermediate scattering function $Fk,t$ is used to obtain theratio of specific heats $\gamma$ and other properties mentioned above. We findthat all of them show non-monotonic variations near the I-N transition, with$\Gamma$ showing a cusp-like behavior. We suggest that the observed anomalousfeatures are a direct consequence of the existence of pseudo-nematic domains inthe system near the phase boundary and the melting and formation of suchdomains give rise to sound attenuation and also to the observed specific heatanomaly. A theoretical description of these anomalies should invoketranslation-rotation coupling at molecular level. While the heterogeneousdynamics observed here bear resemblance to that in deeply supercooled liquidsnear glass transition, the thermodynamic anomalies articulated here are largelyabsent in supercooled liquids.



Autor: Prasanth P. Jose, Biman Bagchi

Fuente: https://arxiv.org/







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