Fréedericksz transition

The Fréedericksz transition is simply a transition from a uniform director configuration to a deformed director configuration upon application of a sufficiently strong magnetic or electric field, note that it is not a phase transition, because at any point in the liquid crystals the amount of order of the molecules relative to one another remains the same. Below a certain field threshold the director remains undistorted. As the field value is gradually increased from this threshold, the director begins to twist until its aligned with the field. In this fashion the Fréedericksz transition can occur in three different configurations known as the twist, bend, and splay geometries. The phase transition was first observed by Fréedericksz and Repiewa in 1927. In this first experiment of theirs, one of the walls of the cell was concave so as to produce a variation in thickness along the cell. The phase transition is named in honor of the Russian physicist Vsevolod Frederiks.