Showing papers by "Samo Kralj published in 1992"
TL;DR: In this paper, the stability of uniaxial nematic-liquid-crystalline structures in supra-m-size spherical cavities that impose a weak homeotropic anchoring is studied theoretically.
Abstract: The stability of uniaxial nematic-liquid-crystalline structures in supra-\ensuremath{\mu}m-size spherical cavities that impose a weak homeotropic anchoring is studied theoretically. The equilibrium equations are obtained with the minimization of the deformation, surface, and field contributions to the free energy and are solved numerically. The dependencies of the solutions on the ratio of elastic constants ${\mathit{K}}_{33}$/${\mathit{K}}_{11}$, ${\mathit{K}}_{24}$/${\mathit{K}}_{11}$, anchoring strength, and external field strength are discussed, and the stability diagrams with lines of structural (Fr\'eedericksz) transitions are constructed. In the region of strong anchoring and large external field strengths, a triple point, where radial, nonsingular axial, and axial structure with the line defect, is predicted. Particular attention is paid to the inversion point corresponding to the critical-field strength above which radial structure is no longer stable. Two possible methods for saddle-splay elastic constant ${\mathit{K}}_{24}$ determination are suggested.
88 citations
TL;DR: In this article, a phenomenological free energy is used to describe the stable ordering of nematic liquid crystals confined to supramicron spherical cavities, and the effects of the saddle splay elastic constant, K 24, on the equilibrium structures and phase diagram of droplets with homeotropic surface anchoring are discussed.
Abstract: A phenomenological free energy is used to describe the stable ordering of nematic liquid crystals confined to supramicron spherical cavities. In particular the effects of the saddle splay elastic constant, K 24, on the equilibrium structures and phase diagram of droplets with homeotropic surface anchoring are discussed. Some structures are illustrated by the corresponding simulated polarization microscope textures. Possibilities for an experimental determination of the saddle-splay elastic constant and surface anchoring strength by studying the radial-axial structural transition in such droplets are analysed. It is shown that the K 24 term in the elastic free energy stabilizes a deformed droplet structure even in the limit of the zero anchoring strength.
37 citations
TL;DR: In this article, the predicted strong dependence of the radial -axial structural transition on the value of the saddlelesplay splay elastic constant K24 is proposed to be used for the indirect determination of this constant.
Abstract: Field induced structural (Freedericksz) transitions in supramicron nematic and cholesteric liquid crystal droplets embedded in a solid matrix are theoretically analysed. Taking into account the elastic, surface, and field free energy contributions, the equilibrium structures and phase diagrams are obtained. The predicted strong dependence of the radial - axial structural transition on the value of the saddlesplay splay elastic constant K24 is proposed to be used for the indirect determination of this constant.
14 citations