Superionic phase transitions, hydrogen bonds

The rearrangement of the hydrogen-bonded network at the superionic phase transitions studied in the framework of the lattice-gas-type model, which has been described in the previous subsection, makes it possible to evaluate the main aspects of proton conductivity in the mentioned compounds. 

Concomitant with the change in the oxygen coordination number is a shift of the first minimum of the O-H RDF from 1.30 A at 34 GPa to 1.70 A at 115 GPa. We observe a similar structural change in the H-H RDF in which the first peak lengthens from 1.63 A (close to the result for ambient conditions) to 1.85 A. These observations bear a strong resemblance to the ice VII to ice X transition in which the covalent O-H bond distance of ice becomes equivalent to the hydrogen bond distance as pressure is increased.82 However, the superionic phase differs from ice X, in that the position of the first peak in g(RoH) is not half the distance of the first 0-0 peak.82 We analyze the effect... 

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