Certain physical properties arise from defects in the ideal ice structure. O bond line. The violation is caused when a water molecule undergoes rotation from one of its six possible orientations to another without compensating adjustments by the adjacent molecules to which it is H-bonded. Such a rotation interchanges some of the molecule's protons and electron pairs. The electrical conduction in ice is carried by the protons, whose motion is closely tied to the motion of ionic defects.
Protonic conduction plays a major role in biological charge transfer processes across membranes.
Proton conduction in ice and H-bonded materials is analogous to electron conduction in semiconductors. The reorientation of the molecular dipoles in ice is facilitated by the mobility of orientational L and D defects, which are generated by thermal activation. Ice is transparent to visible light. It has the lowest index of refraction for the sodium D line of any known crystalline material. It is doubly refracting, uniaxial, optically positive with very small birefringence.