Quantum effects strongly influence the surface premelting of ice

Clear evidence is presented that quantum effects in the motion of the H2O molecules strongly influence the surface premelting of ice. To reveal this behavior, structural and dynamical properties of the ice surface below the melting point were calculated using quantum molecular dynamics with an A initio based force field. The quantum calculations predict the existence of a quasi-liquid-phase that extends for approximately 10 A into the bulk, in agreement with the values obtained by optical ellipsometry experiments. Importantly, surface disorder in the topmost layers of the quantum ice persists at temperatures that are about 10-20 degrees C lower than its classical counterpart, indicating that the surface premelting of ice may largely be a result of quantum effects over a wide range of temperatures.