Effect of hysteresis on the phase transition between high-order commensurate phases

We argue that the phase transition between two high-order commensurate phases and the transition between two modulation wave vectors in the incommensurate phase, can be of the first order. The transition starts from the nucleation of stripple, critical energy of which increases with increasing modulation amplitude. High nucleation energy involves a considerable hysteresis, width of which might even exceed the stability intervals of the high-order commensurate phases. Hence, diffraction measurements made on such states do not allow to detect all high-order commensurate phases.