Crystalline growth of ice – Restructuring of the first wetting layer during multilayer formation

Add to your list(s) Download to your calendar using vCal

• Barbara Lechner, Department of Chemistry, Technical University of Munich, Germany
• Thursday 03 November 2016, 16:00-17:00
• Small Lecture Theatre, Cavendish Laboratory.

If you have a question about this talk, please contact Stephen Walley.

The first water layer on hexagonal single crystal surfaces has a surprisingly complex structure, releasing the strain caused by a mismatch of the ice crystal structure and the substrate lattice by forming rotated hexagons, pentagons and heptagons of molecules in addition to strongly bound hexagonal rings commensurate with the substrate. In a vacuum environment, the water monolayer does not expose any dangling hydrogen bonds and all water molecules adsorb either flat-lying or with a hydrogen atom pointing towards the surface. The growth of the entropically favourable proton-disordered ice, however, requires flipping some of the molecules in the first layer to expose dangling hydrogen bonds. Using scanning tunnelling microscopy (STM) we studied this transition from the first layer to water multilayers on Pt(111) and Ru(0001). We observed that a second water layer initially forms an amorphous structure when grown on the crystalline monolayer containing pentagons, hexagons and heptagons of water molecules. To facilitate the growth of ice in a bulk-like hexagonal arrangement, the first wetting layer needs to rearrange into a hexagonal structure commensurate with the surface. Complementary STM measurements confirmed the facile re-orientation of certain molecules in the water monolayer on Pt(111) upon adsorption of ammonia (NH3) molecules. We found that NH3 binds preferentially to H2O molecules that are slightly elevated from the surface and weakly bound to the metal. Ammonia molecules thus detect locations in the wetting layer where a water molecule can change its orientation relatively easily to flip up a hydrogen atom.

This talk is part of the Physics and Chemistry of Solids Group series.

This talk is included in these lists:

• All Cavendish Laboratory Seminars
• All Talks (aka the CURE list)
• Centre for Health Leadership and Enterprise
• Featured lists
• ME Seminar
• Neurons, Fake News, DNA and your iPhone: The Mathematics of Information
• Physics and Chemistry of Solids Group
• School of Physical Sciences
• Small Lecture Theatre, Cavendish Laboratory
• Thin Film Magnetic Talks

Note that ex-directory lists are not shown.