Bjerrum faults

Molecular reorientations at Bjerrum fault sites are responsible for the dielectric properties of ice. A second type of fault (proton jumps from one molecule to a neighbor) accounts for the electrical conductivity of ice, but cannot account for the high dielectric constant of ice. Further discussion of such ice faults is provided by Franks (1973), Franks and Reid (1973), Onsager and Runnels (1969), and Geil et al. (2005), who note that interstitial migration is a likely self-diffusion mechanism. 

In Section A, we have already considered the approach that includes the movement of two types of faults ionic state (positive or/and negative) and Bjerrum faults. It has been suggested (see also, e.g., Refs. 158-160) that the drift of the ionic state (i.e., strictly speaking, an excess proton or proton hole) along the ordering chain changes the polarization of each site and therefore changes the polarization of the whole chain. 

Thus, for the motion of the next state along the chain it is necessary to repolarize the chain into its initial state, which can be achieved by Bjerrum-fault transfer. The semiphenomenological theory of proton transfer along the hydrogen-bonded chain of the ice-like structure, developed in Ref. 161, includes the influence of longitudinal acoustic vibrations of the chain sites on the proton subsystem. Reference 162, in which the dynamics of the ionic state formation in the hydrogen-bonded chains is considered, resembles roughly Ref. 161. 

Let us suppose that the strong hydrogen-bonded chain is absolutely ordered either by a strong external electric field 8 or by the asymmetrical arrangement of side bonds (Fig. 8). Then we assume that thermally activated structural defects in a hydrogen-bonded chain (like those in ice) are practically excluded (in the similar structure system—that is, ice—the concentration of Bjerrum faults is 5x 10-7 per molecule H20, and the concentration of ions is 10-12 per molecule H20 [159]). 

Dougherty (/. Chem, Phys, 43 (9), 3247, 1965) extended the theory to include interactions between Bjerrum faults and their eflFect on relaxation in pure ice. He concluded that this effect is small. It may, however, be considerable in HF ice. The interaction between ions and their atmosphere of Bjerrum faults is more important in an analytic treatment of ice conductivity. 

Bjermm defects act as catalysts to promote dipole turns, with one fault for every 106 molecules, corresponding to a turn rate of 10-12 s-1 at an orientation fault site. Devlin and coworkers (Wooldridge et al 1987) suggested that Bjerrum defects are essential to the growth of hydrates from the vapor phase. 

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