The lone proton migration mechanism translocation

The translocation mechanism is shown in Fig. 1.1a, b. It results from the coupling of (a) displacement of along a hydrogen bond and (b) transport of the H ion from this hydrogen bond to the following one. Such a mechanism can occur only in the presence of L defects, as shown in the Bjerrum theory of ice conductivity (reference 15 and 

Chapters 10 and 11). In this theory, the occurrence of doubly occupied sites (Doppelsetzung, D) and/or empty sites (Lehrstehle, L) in a translocation mechanism (Fig. 1.1b) is postulated. 

The necessity of having Bjerrum defects present is illustrated for the network of water molecules in Fig. 1.1c. From (i) to (ii), two transfers occur simultaneously, in a chain sequence under the influence of an applied field V. In (ii) however, this has resulted in the creation of a reverse field, V which induces the protons to hop back to their original position. Consequently, long-range H conduction cannot occur. 

Consider now, in Fig. 1.1c (iii), the effect of allowing the central water molecule in the network to rotate. This creates a pair of L and D defects in adjacent hydrogen bond positions and, on departure of from the vicinity of this L, D couple, the V field is destroyed. Conduction can clearly continue, therefore, and the arrival of a new ion from the left restores the chain element in (iv) to its original position (i). 

Four types of translocation have been proposed . These are as follows. 

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