Ice and Bjerrum defects

FIGURE 2.1 Basic crystal structure for ice Ih. (Reproduced from Durrant, P.J., Durrant.B., Introduction to Advanced Inorganic Chemistry, John Wiley Sons, Inc., New York (1962). With permission.) 

The ice crystal structure consists of water molecules hydrogen-bonded in a solid lattice. Since water molecules are similarly bonded in hydrates, both water molecules and hydrogen bonds are considered briefly in the following two sections. Many mechanical properties of ice are similar to hydrates, as detailed in Section 2.2. 

FIGURE 2.2 (a) Two-dimensional proton-disordered ice lattice (Bjerrum defect illustrated 

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. 

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. 

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