All domains are assumed to have polarization of the same magnitude Ps, but the polarization can have different orientations. The applied electric field changes the domain orientation, and the resulting net polarization in the ferroelectric material is found from the following nonlinear implicit relation:
where the matrix α characterizes the interdomain coupling.
where the reversibility is characterized by the matrix cr, and the anhysteretic polarization is found from a relation similar to
Equation 2-8: