  We study the core structure of the twist-grain-boundary (TGB) phase of chiral
liquid crystals by numerically minimizing the Landau-de Gennes free energy. We
analyze the morphology of layers at the grain boundary, to better understand
the mechanism of frustration between the smectic layer order and chirality. As
the chirality increases, the effective bending rigidity of layers is reduced
due to unlocking of the layer orientation and the director. This results in
large deviation of the layer morphology from that of Scherk's first minimal
surface and linear stack of screw dislocations (LSD).
