Twist disclinations in thin SmC* liquid crystal

In thin samples of SmC* liquid crystals where the planar boundary conditions unwound the helical structure but induce a twist in smectic layers along the sample thickness, a 2π-twist disclination can occur in order to mediate the parts of sample with opposite sense of twist. The anisotropy of the twist disclination self-energy is investigated. The splitting of the 2π-surface twist disclination into two 2π-twist disclinations is proposed within the Peierls-Nabarro model of the disclination core. From this splitting the surface anchoring energies are estimated. The proposed models are confirmed by the optical observations of 2π-twist disclinations.