Ice formation in aqueous systems

SUMMARY A recent treatment of the energetics of homogeneous nucleation brings classical nucleation theory into conformity with classical thermodynamic limits for supersaturated phase stability called spinodals. This energetic treatment, when extended to crystal nucleation from the liquid state, predicts that nucleation of ice cannot be avoided simply by rapid quenching. Nucleation will occur on cooling an aqueous system to a temperature called the physical spinodal because at and below this temperature icelike clusters in the aqueous system can grow without any free energy barrier whatsoever. Interpretation of microscopic observations of rapidly quenched biological systems must account for the fact that ice nuclei are certain to have been present throughout.