The microstructure of a ferroelectric single crystal is significantly affected by applied loads. Domains evolve through equilibrium states, following a route that minimizes the overall energy. The herringbone pattern is one of the most widely observed domain structures in ferroelectric crystals. In this work, the evolution of four types of herringbone pattern in the tetragonal crystal system is studied by using a variational method. These four herringbone patterns are periodic rank-2 laminate...