Intergranular liquid in solids and premelting of ice

That the equilibrium state of impurity-free polycrystalline ice contains water has been expressed in terms of free-energy changes, and further developed to show that liquid in cavities formed at grain junctions in a microcrystalline solid containing no impurities affects its electrical properties and increases its heat capacity. General formulas for the volume of a liquid contained in the pockets formed at four-grain junctions and veins formed at three-grain junctions in equilibrium in an impurity-free polycrystalline mass are given. The variation of the volume fraction of intergranular water in impurity-free ice and the ice’s total free energy have been calculated for different grain sizes and temperatures. Calculations also confirm that intergranular water or premelting contributes significantly to the pure ice’s heat capacity.