Phase transition and water molecules in titanylphthalocyanine phase Y crystal

We have performed several experiments and molecular dynamics calculations t o investigate a phase transition of titanylphthalocyanine phase Y crystal a nd the behavior of water molecules in the crystal. We have shown that water is in the crystal as well as on its surface and the humidity dependence of the photosensitivity of the phase Y is due to the water on the surface. We propose a mechanism for the phase transition from the metastable phase Y t o a stable phase I as follows. Water molecules on the surface detach as the crystal is heated to 100 degreesC. At about 250 degreesC water molecules i n the crystal begin to jump from one space to another through channels conn ecting the spaces and as a result are expelled from the crystal. After the water molecules leave the spaces, the phase transition to phase I occurs by molecular rearrangement to shrink these spaces.