Liquid-Crystal Smectic with Six-Layer Periodic Structure

Recently Wang et al. [Phys. Rev. Lett. 104, 027801 (2010)] discovered a new polar smectic phase with six-layer period (SmC*d6). In this manuscript, we demonstrate that the theory [Phys. Rev. E 67, 041716 (2003)] based on the free energy expansion with a two-component order parameter predicted the six-layer phase, describes its structure and the phase sequence observed in experiment [Phys. Rev. Lett. 104, 027801 (2010)].