Antiphase structures in polar smectic liquid crystals and their molecular origin

We demonstrate that the overall molecular dipole organization in a smectic liquid crystal formed of polar molecules can be strongly influenced by the position of the dipole in the molecule. We study by large scale Monte Carlo simulations systems of attractive-repulsive ''Gay-Berne'' elongated ellipsoids with an axial dipole at the center or near the end of the molecule and we show that monolayer smectic liquid crystals and modulated antiferroelectric bilayer stripe domains similar to the experimentally observed ''antiphase'' structures are obtained in the two cases.