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Latent heat of crystallization of amorphous ice

  Crystallization of amorphous ice triggered by radiogenic heating is another heating mechanism. When amorphous ice crystallizes, latent heat is released, because a crystalline state is more stable than an amorphous state. However, there is an energy barrier called an activation energy for the transition of amorphous ice to crystalline ice. The situation is illustrated in Fig. 7.

For the transition of amorphous ice to crystalline ice I (cubic ice), we take the latent heat tex2html_wrap_inline1564 (Ghormley, 1968), and the activation energy tex2html_wrap_inline1566 per H tex2html_wrap_inline1146 O molecule (Schmitt et al., 1989). In terms of temperature, tex2html_wrap_inline1570 K and E/k=5370,K, where tex2html_wrap_inline1574 is mass of an H tex2html_wrap_inline1146 O molecule.

The rate of the transition from amorphous to crystalline ice at temperature T may be expressed by

  equation313

where A is a constant and is given by tex2html_wrap_inline1582 s for a transition from amorphous ice to crystalline (cubic) ice (Schmitt et al., 1989). The value of tex2html_wrap_inline1584 of tex2html_wrap_inline1586 is on the order of the lattice vibration frequency. It should be noted from eq. (10) that the rate of crystallization rapidly increases with increasing temperature, since tex2html_wrap_inline1588 in the relevant temperatures. Theoretical derivation of eq. (10) is given by Kouchi et al. (1994).


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Mon Sep 16 16:23:29 JST 1996