Question

Why does krypton form crystals at sufficiently low temperatures despite having no
permanent dipole moments?

Answer 1

Thermotropic phases are those that occur in a certain temperature range.
If the temperature rise is too high, thermal motion will destroy the delicate cooperative ordering of the LC phase, pushing the material into a conventional isotropic liquid phase.
At too low temperature, most LIQUID CRYSTALS materials will form a conventional crystal. Many thermotropic LCs exhibit a variety of phases as temperature is changed.
For instance, a particular type of LC molecule (called mesogen) may exhibit various smectic and nematic (and finally isotropic) phases as temperature is increased.
An example of a compound displaying thermotropic LC behavior is para-azoxyanisole.

It has a non-equilibrium phase which can only form at low temperatures, where the driving force for the reaction is sufficient to overcome the considerable lattice strain imposed by the transformation.
The transformation is essentially time-independent with the phase fraction depending only the degree of cooling below the critical martensite start temperature