http://localhost:80/xmlui/handle/123456789/188 2026-04-08T12:31:52Z http://localhost:80/xmlui/handle/123456789/193 Title: A molecular field approach to pressure-induced phase transitions in liquid crystals: Smectic–nematic transition Authors: DasGupta, Sudeshna Abstract: Since a rigorous microscopic treatment of a nematic fluid system based on a pairwise interaction potential is immensely complex, we had introduced a simple mean field potential, which was a modification of the Maier–Saupe potential in a previous paper [S. DasGupta et al., “Pressure-induced phase transitions in liquid crystals: A molecular field approach,” Phys. Rev. E 98, 022701 (2018)]. Building upon that, here we have modified that potential to take into account the various aspects of a smectic A–nematic phase transition. In particular, we have studied the dependence of the phase transition on the coupling coefficient between the nematic and smectic order parameters, which in turn depends on the length of alkyl chain, variation of density, entropy, and specific heat. Detailed investigation on the coupling parameter shows the existence of a smectic A–nematic–isotropic triple point as well as a tricritical point where the smectic–nematic phase transition changes its nature from the second to the first order. It is also seen that the application of pressure can result in the appearance of a nematic phase. Description: Physics of Fluids special topic : Tribute to Frank M. White on his 88th Anniversary. 2021-01-01T00:00:00Z http://localhost:80/xmlui/handle/123456789/192 Title: Monte Carlo study with reweighting of uniaxial nematic liquid crystals composed of biaxial molecules Authors: DasGupta, Sudeshna Abstract: We present a high accuracy Monte Carlo simulation study of the uniaxial nematic (N U ) to isotropic (I) phase transition of a lattice dispersion model of uniaxial nematics composed of biaxial molecules. The N U -I coexistence curve terminating at the Landau critical point has been determined using the multiple histogram reweighting technique. A close investigation reveals a sharp departure in the nature of the N U -I coexistence curve in the temperature-biaxiality parameter phase diagram in comparison to the earlier theoretical (either mean-field or computer simulation) predictions. The coexistence curve shows a change in curvature with increasing value of the degree of molecular biaxiality. 2019-01-01T00:00:00Z http://localhost:80/xmlui/handle/123456789/191 Title: Pressure-induced phase transitions in liquid crystals: A molecular field approach Authors: DasGupta, Sudeshna Abstract: A rigorous microscopic treatment of a nematic fluid system based on a pairwise interaction potential is immensely complex. For studying such systems molecular field theories are often the standard method of 2 P 2 P 2 (cos ϑ ) to study choice. In this paper we have chosen a simple effective potential U = u v 4 4 − u v 2 2 − Au v 2 an isothermal-isobaric ensemble describing a liquid crystalline system. Using this we have studied in particular the pressure dependence of liquid crystalline phase transitions. 2018-01-01T00:00:00Z http://localhost:80/xmlui/handle/123456789/190 Title: Monte Carlo investigation of critical properties of the Landau point of a biaxial liquid-crystal system Authors: DasGupta, Sudeshna Abstract: Extensive Monte Carlo simulations are performed to investigate the critical properties of a special singular point usually known as the Landau point. The singular behavior is studied in the case when the order parameter is a tensor of rank 2. Such an order parameter is associated with a nematic-liquid-crystal phase. A three-dimensional lattice dispersion model that exhibits a direct biaxial nematic-to-isotropic phase transition at the Landau point is thus chosen for the present study. Finite-size scaling and cumulant methods are used to obtain precise values of the critical exponent ν = 0.713(4), the ratio γ /ν = 1.85(1), and the fourth-order critical Binder cumulant U ∗ = 0.6360(1). Estimated values of the exponents are in good agreement with renormalization-group predictions. 2016-01-01T00:00:00Z