MOLECULAR-SURFACE STRUCTURE OF A LOW-TEMPERATURE ICE IH(0001) CRYSTAL

An ice film with thickness greater than 10 Angstrom was crystallized o n a clean Pt(111) surface. Its external surface structure was investig ated at 90 K by dynamical low-energy electron diffraction (LEED), foll owed by molecular dynamics simulations and ab initio quantum chemical calculations. The results favor the common hexagonal ice Ih structure over other forms of ice, with (0001) termination. A full-bilayer termi nation is found, but with much enhanced amplitudes of motion of the O atoms in the outermost layer of H2O molecules, even at 90 K, so that t hese molecules were undetected experimentally by LEED.