A calculation of the equilibrium polarization and of the piezoelectric and pyroelectric coefficients of β-phase poly(vinylidene fluoride) (PVF2) is presented. The effects of both the orthorhombic crystal structure and of the finite separation between the monopoles of the molecular dipole are taken into account. Good agreement is obtained with the experimentally measured polarization and piezoelectric and pyroelectric coefficients of β-PVF2 films.
A theoretical study is made of the process by which an antiferroelectric smectic liquid crystal undergoes a field-induced transition to ferroelectric alignment. We find that for cells of moderate thickness the initial departure from antiferroelectric alignment occurs as a continuous Fréedericksz transition. The following transition from partial alignment to complete ferroelectric ordering may occur as either a first-order or continuous transition, depending on the relative strength of some of the model parameters. The case where the transition is continuous provides a possible mechanism for some recently observed thresholdless transitions in these systems.
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