IUCr journals

Enantiotropic phase transition and twinning in 2,2,3,3,4,4-hexafluoropentane-1,5-diol

Acta Cryst. (2009). C65, o388–o395 (doi.org/10.1107/S0108270109025141)

[Sliding of layers during phase transition] The superposition of (012) layers of two forms is presented to illustrate sliding of the layers during the enantiotropic phase transition of HFPD.
The organic compound 2,2,3,3,4,4-hexafluoropentane-1,5-diol (HFPD) was found to undergo a temperature-dependent phase transition between two closely related triclinic polymorphs. Each of the two phases is twinned with either two or four individuals depending on the temperature cycling history. The molecules form sheets that slide with respect to others during the phase transition. The phase transition is triggered by the natural contraction of the unit cell upon cooling coupled with several unfavorable C-H···F and F···F non-bonded contacts.

J.-M. Ha and V. Young