Factors that control the morphology of ice films on metal surfaces

Examination of the equilibrium nanoscale morphology of ice films provides important clues about the energetics of water-metal interactions [1]. In this talk I compare STM and DFT results for the structure of ice films on Pt(111) and Ni(111). Because the lattice constants of Ni and Pt differ by 10{\%}, this comparison allows us to probe the effect of lattice misfit on ice nucleation and growth. On both substrates, STM suggests a first molecular water layer very different from bulk ice: besides the usual hexagonal rings they also both contain a motif of pentagons and heptagons [2]. Furthermore, at 140K, thicker films on both substrates dewet the substrate to lower interfacial energy by forming 3-dimensional ice crystallites several nanometers thick [3]. However, despite these similarities, there are striking differences in the submonolayer structure and in the kinetics of the dewetting process. Using DFT calculations as a guide, I will discuss the how these differences can be related to substrate lattice constant and draw conclusions about the processes that control ice film morphology. \\[4pt] [1] A. Hodgson and S. Haq, Surf. Sci. Rep. 64, 381 (2009). \\[0pt] [2] S. Nie, P. J. Feibelman, N. C. Bartelt and K. Th\"{u}rmer, Phys. Rev. Lett. 105, 026102 (2010). \\[0pt] [3] K. Th\"{u}rmer and N. C. Bartelt, Phys. Rev. B 77, 195425 (2008); Phys. Rev. Lett. 100, 186101 (2008).