Roughening transition of prism faces of ice crystals grown from melt under pressure

By observing the crystal shapes and kinetics of ice Ih growing at high pressures from the melt, it was found that the prism {101¯0} faces undergo a roughening transition at approximately -16∘C and 160 MPa (1600 bar) in H2O ice, and -14∘C and 180 MPa (1800 bar) in D2O ice. At temperatures above the roughening transition, the prism facets completely vanished and the curves of growth rate versus growth drive were linear. In contrast, below the roughening temperature, regions of prism facets existed and the growth rate curves were approximately quadratic. The basal {0001} faces persisted up to 0∘C and gave approximately quadratic growth rate curves. The melting curves of ice Ih for H2O and D2O were accurately measured by direct observations of the solid-liquid coexistence equilibrium and found to agree with previous results obtained with other methods.