Orientational dynamics and energy landscape features of thermotropic liquid crystals: an analogy with supercooled liquids

Jana, Biman ; Bagchi, Biman (2007) Orientational dynamics and energy landscape features of thermotropic liquid crystals: an analogy with supercooled liquids Journal of Chemical Sciences, 119 (5). pp. 343-350. ISSN 0253-4134

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Official URL: http://www.ias.ac.in/chemsci/Pdf-Sep2007/343.pdf

Related URL: http://dx.doi.org/10.1007/s12039-007-0045-1

Abstract

Recent optical kerr effect (OKE) studies have revealed that orientational relaxation of rodlike nematogens near the isotropic-nematic (I-N) phase boundary and also in the nematic phase exhibit temporal power law decay at intermediate times. Such behaviour has drawn an intriguing analogy with supercooled liquids. Here, we have investigated the single-particle and collective orientational dynamics of a family of model system of thermotropic liquid crystals using extensive computer simulations. Several remarkable features of glassy dynamics are on display including non-exponential relaxation, dynamical heterogeneity, and non-Arrhenius temperature dependence of the orientational relaxation time. Over a temperature range near the I-N phase boundary, the system behaves like a fragile glass-forming liquid. Using proper scaling, we construct the usual relaxation time versus inverse temperature plot and explicitly demonstrate that one can successfully define a density dependent fragility of liquid crystals. The fragility of liquid crystals shows a temperature and density dependence which is remarkably similar to the fragility of glass forming supercooled liquids. Energy landscape analysis of inherent structures shows that the breakdown of the Arrhenius temperature dependence of relaxation rate occurs at a temperature that marks the onset of the growth of the depth of the potential energy minima explored by the system.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Liquid Crystals; Supercooled Liquid; Power Law Relaxation; Fragility; Heterogeneous Dynamics; Energy Landscape
ID Code:3993
Deposited On:13 Oct 2010 07:05
Last Modified:16 May 2016 14:40

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