Electron induced restructuring of crystalline ice adsorbed on Pt(1 1 1)

Water adsorbs on Pt(1 1 1) at 137 K to form a series of ordered hexagonal bilayer structures. At submonolayer coverages the ice coalesces to form islands with an (37×37)R25.3° structure which are relatively stable to low energy electrons. At saturation the overlayer compresses to form a (39×39)R16.1° overlayer. Further water condenses on this template to grow multilayers which become metastable with respect to an incommensurate bulk ice film. The √39 structure is unstable to electron exposure, a monolayer film restructuring to form islands of incommensurate bulk ice and exposing bare Pt. As the ice film becomes thicker, the lateral stress increases and relaxation becomes fast. Workfunction measurements show no evidence for any preferential alignment of the water dipole in the epitaxial phases, as compared to bulk ice, indicating that the films are proton disordered. Stress in the epitaxial overlayer is due to the lateral compression which maximises the binding of the first layer to Pt, rather than an ordering of the water dipoles.