Layered phase: 1D positional order + orientational order, focal conic defects
Smectics have 1D positional order: molecules arrange in layers of spacing d ~ 30Å. The Helfrich-Hurault instability buckles layers when a magnetic/electric field exceeds a threshold. Focal conic domains are the hallmark defect structures. Tilt of the director away from the layer normal drives the Sm-A→Sm-C transition.