Large-facetted monocrystals of blue phase I are grown and observed in coexistence with the isotropic liquid. Observations of this three-dimensional polyhedral habit, combined with a conjecture that facets perpendicular to screw axes are absent, are compatible with the $I\left(4_{1}32\right)$ space group for blue phase I. The (200) planes Bragg reflect approximately the same wavelength as the cholesteric spiral indicating that the blue phase I lattice constant is the cholesteric pitch even very close to the isotropic phase.

• Received 29 March 1984

DOI:https://doi.org/10.1103/PhysRevA.30.1161