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Author

Shri Singh

Other affiliations: University of Guelph
Bio: Shri Singh is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Liquid crystal & Phase transition. The author has an hindex of 18, co-authored 97 publications receiving 1446 citations. Previous affiliations of Shri Singh include University of Guelph.


Papers
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Book ChapterDOI
01 Jan 2016
TL;DR: A comprehensive overview of polymer dispersed liquid crystal (PDLC) studies can be found in this paper, where a brief discussion on the current scenario of dispersion studies in liquid crystals is presented.
Abstract: During the last three decades intense studies have been carried out to understand the behavior of liquid crystals dispersed in various media. One of the most common outcomes is the polymer dispersed liquid crystals (PDLCs), in which liquid crystal droplets are dispersed in an appropriate polymer matrix. The investigation of PDLCs is of immense significance because of their strong potential for scientific and technological applications and basic understanding. The current article presents a comprehensive overview till date of the some important developments in this field. We begin with a brief discussion on the current scenario of dispersion studies in liquid crystals which is followed by the description of preparation, morphology, characterization and some important properties of PDLCs. Recent advancements such as PDLCs with conducting polymers, holographic PDLCs and influence of foreign elements on the properties of PDLCs are also covered. The remaining parts are concerned with the time dependent phenomenon and theoretical developments. A survey of some of their applications is also given. The article ends with a brief comment on future perspective and challenges.

13 citations

Journal ArticleDOI
TL;DR: In this article, a phenomenological model to describe the general features of chiral smectic C* (Sm C*) phase and Sm A-Sm C* phase transition properties of ferroelectric liquid crystals is presented.
Abstract: We construct a phenomenological model to describe the general features of chiral smectic C* (Sm C*) phase and Sm A–Sm C* phase transition properties of ferroelectric liquid crystals The free-energy density of the system is expanded in terms of three degrees of freedom – tensor orientational order Q ij , scalar smectic order Ψ and polarization vector P and couplings between these order parameters Since Q ij describes the tilt vector ξ, no term contains ξ The values of Landau coefficients are determined by comparing with the experimental data of helical pitch, tilt angle and spontaneous polarization and introducing an empirical relation for the temperature variation of the modulus S of orientational order parameter Q ij Taking these values we evaluate the tilt angle, spontaneous polarization and pitch of the Sm C* phase and the Sm A–Sm C* phase transition It is found that the theoretical results agree very well with the experimental data of four ferroic mesogens

12 citations

Journal ArticleDOI
13 Nov 2012-EPL
TL;DR: In this article, Monte Carlo simulations of ordering dynamics in d = 2 nematic liquid crystals are presented, and the numerical and analytical results are in excellent agreement, showing that the domain growth law is consistent with L(t) ~ (t/ln t)1/2.
Abstract: We present comprehensive results from Monte Carlo (MC) simulations of ordering dynamics in d = 2 nematic liquid crystals. We compare our MC results with an analytic form obtained for the correlation function of the liquid crystal order parameter. The numerical and analytical results are in excellent agreement. The domain growth law is consistent with L(t) ~ (t/ln t)1/2.

12 citations

Journal ArticleDOI
TL;DR: In this article, rare gas collision-induced far infrared absorption spectra have been simulated classically at three reduced temperatures, T* = 4, 2, 1, and T * = 1.
Abstract: Rare gas collision-induced far infrared absorption spectra have been simulated classically at three reduced temperatures, T* = 4, 2, 1. At the lowest temperature (T* = 1), bound states make a significant contribution (20 per cent). The results are compared to an asymptotic theory of the line shape. The agreement is perfect in the wings of the line, as expected, but is also surprisingly good at lower frequencies.

11 citations

Journal ArticleDOI
TL;DR: It is found that systems with n = 2 show the same dynamical behavior as the nearest-neighbor case (n = ∞), which contradicts available theoretical predictions.
Abstract: We present the results from comprehensive Monte Carlo (MC) simulations of ordering kinetics in d = 2 liquid crystals (LCs) Our LC system is described by the two-component Lebwohl-Lasher model with long-ranged interactions, V(r) ∼ r -n We find that systems with $n \geq 2$ show the same dynamical behavior as the nearest-neighbor case (n = ∞ This contradicts available theoretical predictions

11 citations


Cited by
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Journal ArticleDOI
TL;DR: This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices.
Abstract: Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given (234 references).

1,278 citations

Journal ArticleDOI
TL;DR: This Review focuses on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade, and the developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc.
Abstract: Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photoc...

576 citations

Book ChapterDOI
TL;DR: The main objective of field-cycling experiments [231, 367] is to obtain information on the spectral density of the fluctuating spin interactions in a frequency range as wide as possible as mentioned in this paper.

547 citations

Journal ArticleDOI
TL;DR: Recent results help elucidate structure and hydrogen-bonded interactions, as well as showcase a successful interplay between theory and experiment in gas-phase spectroscopy.
Abstract: Gas-phase spectroscopy lends itself ideally to the study of isolated molecules and provides important data for comparison with theory. In recent years, we have seen enormous progress in the study of biomolecular building blocks in the gas phase. The motivation for such work is threefold: (a) It is important to distinguish between intrinsic molecular properties and properties that result from the biological environment. (b) Gas-phase spectroscopy of clusters provides insights into fundamental interactions and into microsolvation. (c) Gas-phase data support quantum-chemical calculations. This review focuses on the current status of (poly)amino acids and DNA bases. Recent results help elucidate structure and hydrogen-bonded interactions, as well as showcase a successful interplay between theory and experiment.

359 citations

Journal ArticleDOI
TL;DR: Different strategies commonly used to formulate the free-energy functional of complex fluids for either phenomena-oriented applications or as a generic description of the thermodynamic nonideality owing to various components of intermolecular forces are discussed.
Abstract: Density-functional theory (DFT) and its variations provide a fruitful approach to the computational modeling of the microscopic structures and phase behavior of soft-condensed matter. The methodology takes deep root in quantum mechanics but shares a mathematical similarity with a number of classical approaches in statistical mechanics. This review discusses different strategies commonly used to formulate the free-energy functional of complex fluids for either phenomena-oriented applications or as a generic description of the thermodynamic nonideality owing to various components of intermolecular forces. We emphasize the connections among different schemes of DFT approximations, their underlying assumptions, and inherent limitations. We also address extensions of equilibrium DFT to phenomenological theories for the dynamic properties of complex fluids and for the kinetics of phase transitions. In addition, we highlight the recent literature concerning applications of DFT to diverse static and time-dependent phenomena in complex fluids.

343 citations