  General microscopic mechanism of ferroelectric ordering in chiral smectic C*
liquid crystals is considered. It is shown that if the mesogenic molecules have
a sufficiently low symmetry, the spontaneous polarization is proportional to
one of the biaxial vector order parameters of the smectic C phase. This order
parameter may be determined by intermolecular interactions which are not
sensitive to molecular chirality. At the same time, the polarization is also
proportional to a pseudoscalar parameter which vanishes if the molecules are
nonchiral. The general statistical theory of ferroelectric ordering is
illustrated by two particular models. The first model is based on electrostatic
quadrupole-quadrupole interactions, and it enables one to obtain explicit
analytical expressions for the spontaneous polarization. In the second model,
the molecular chirality and polarity are determined by a pair of off-center
nonparallel dipoles. For this case, the spontaneous polarization is calculated
numerically as a function of temperature. The theory provides a more general
interpretation of the previous approaches including the classical Boulder
model.
