Defects and conduction mechanism

Ideally, ice has the structure described above and it can easily be seen that it is impossible for protons to move in it, since such motion would violate the Bemal-Fowler rules. However, at all real temperatures there 

The activation energy of conductivity equals the activation energy of defect creation which therefore indicates a nonactivated character for proton motion along the bonds. 

Notwithstanding the fact that motion of ionic defects is connected with the motion of protons, it does not imply a real proton transfer. Actually there occur only successive local displacements of protons along the bonds. Due to the memory of the protonic system, after a certain amount of current has passed, all the bonds appear to be blocked, and further passage of current is impossible. It should be remembered however, that there are also defects of the second type in the system, namely, D and L defects, shown in Fig. 10.2, which represent violations of the first Bernal-Fowler rule. A D defect moving in the same direction as an defect, polarizes the bonds in the opposite direction, that is, it unblocks them as seen in Fig. 10.2. In an analogous way the motions of OH and L defects are related. So, by a combined motion of all the defects (or of only an D pair) a current may pass through ice indefinitely. D and 

L defects have effective charges + 0.38c. Their mobilities at a temperature r= 253K equaF 

These values of partial conductivities do not take into account the interaction via polarization of the bonds. During the motion of all four types of the defects such interaction leads to a frequency dependence of the overall conductivity 

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