Thermodynamic stability of hexagonal and cubic ices

The thermodynamic stability of hexagonal and cubic ices are examined by evaluating the free energies of those two phases over a wide range of temperature. One hundred proton-disordered configurations are generated for each form of ice, and a lattice dynamics calculation is applied. It is shown that the free energy of hexagonal ice is about 100 J mol−1 lower than that of cubic ice, and therefore more stable in the calculated temperature range (53–273 K). This is an agreement with experiment.