抄録
In antiferroelectric smectic materials, it is expected that the tilt angle influences not only on stability of the antiferroelectric phase but also on the one of intermediate phases. The effects of the tilt angle θ and dipole-dipole interaction on the stabilities of phases are studied on the base of the molecular interactions in smectics. It is shown that in θ < θ_c (θ_c : a critical angle), the behavior of XY-symmetry is stable, while in θ > θ_c, the one of Ising-symmetry is stable.