Constrained modeling of domain patterns in rhombohedral ferroelectrics

A nonconventional phase-field model is developed to predict ferroelectric domain structures. It employs a set of field variables motivated by multirank laminates to represent energy-minimizing domain configurations, giving rise to an explicit expression of the energy-well structure. The framework is applied to domain simulation in the rhombohedral phase assuming that polarization is close to the ground states. An electromechanical self-accommodation pattern consisting of eight rhombohedral variants and an engineered domain configuration are predicted and found in good agreement with those observed in experiment.