Molecular surface structure of ice(0001): Dynamical low-energy electron diffraction, total-energy calculations and molecular dynamics simulations

A structural study of the surface of an ultrathin ice film grown on a Pt(lll) substrate was performed using dynamical low-energy electron diffraction (LEED) at 90 K, together with total-energy calculations and molecular dynamics (MD) simulations. This ice film exhibits the common hexagonal phase Ih and exposes the (0001) surface without reconstruction. The surface is terminated as a full-bilayer that maximizes the number of surface hydrogen bonds as confirmed by our total-energy calculations. Both LEED and MD simulations End that the outermost water molecules have enhanced vibrational amplitudes making them practically undetectable by LEED even at 90 K. MD simulations of the half-bilayer terminated surface yield results inconsistent with the LEED findings, thus excluding this model. (C) 1997 Elsevier Science B.V.