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Energy landscape view of phase transitions and slow dynamics in thermotropic liquid crystals

Chakrabarti, Dwaipayan and Bagchi, Biman (2006) Energy landscape view of phase transitions and slow dynamics in thermotropic liquid crystals. In: Proc Natl Acad Sci Unit States Am, 103 (19). pp. 7217-7221.

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Official URL: http://www.pnas.org/content/103/19/7217.short

Abstract

Thermotropic liquid crystals are known to display rich phase behavior on temperature variation. Although the nematic phase is orientationally ordered but translationally disordered, a smectic phase is characterized by the appearance of a partial translational order in addition to a further increase in orientational order. In an attempt to understand the interplay between orientational and translational order in the mesophases that thermotropic liquid crystals typically exhibit upon cooling from the high-temperature isotropic phase, we investigate the potential energy landscapes of a family of model liquid crystalline systems. The configurations of the system corresponding to the local potential energy minima, known as the inherent structures, are determined from computer simulations across the mesophases. We find that the depth of the potential energy minima explored by the system along an isochor grows through the nematic phase as temperature drops in contrast to its insensitivity to temperature in the isotropic and smectic phases. The onset of the growth of the orientational order in the parent phase is found to induce a translational order, resulting in a smectic-like layer in the underlying inherent structures; the inherent structures, surprisingly, never seem to sustain orientational order alone if the parent nematic phase is sandwiched between the high-temperature isotropic phase and the low-temperature smectic phase. The Arrhenius temperature dependence of the orientational relaxation time breaks down near the isotropic-nematic transition. We find that this breakdown occurs at a temperature below which the system explores increasingly deeper potential energy minima.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to National Academy of Sciences.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 13 Jul 2010 10:07
Last Modified: 19 Sep 2010 06:10
URI: http://eprints.iisc.ernet.in/id/eprint/28882

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