Instability of the lattice structure of crystalline liquids near the BPI-BPII phse transition

Essential change of the splitting between reflections (200) and (110) with temperature in the Blue Phase I (BPI) transmission spectrum in an electric field has been observed. The electrostriction coefficient $\gamma_{1111}$ in BPI increases anomalously, while approaching the BPI-BPII phase transition temperature. These results show that the phase transition is connected with lattice instability with increasing temperature