The molecular structure of the H2O wetting layer on Pt(111)

TL;DR

This study uses scanning tunneling microscopy to resolve the molecular structures of water ice wetting layers on Pt(111), revealing temperature-dependent superstructures and reversible transformations.

Contribution

It provides the first direct imaging of the molecular arrangements of water wetting layers on Pt(111), identifying two distinct superstructures and their reversible transformations.

Findings

Identified two superstructures: sqrt(37) x sqrt(37) R25.3° at 140K and sqrt(39) x sqrt(39) R16.1° at 130K.

Observed reversible transformation between superstructures with temperature and coverage changes.

Revealed complex molecular geometries within the superstructures.

Abstract

The molecular structure of the wetting layer of ice on Pt(111) is resolved using scanning tunneling microscopy (STM). Two structures observed previously by diffraction techniques are imaged for coverages at or close to completion of the wetting layer. At 140K only a sqrt(37) x sqrt(37) R25.3{\deg} superstructure can be established, while at 130K also a sqrt(39) x sqrt(39) R16.1{\deg} superstructure with slightly higher molecular density is formed. In the temperature range under concern the superstructures reversibly transform into each other by slight changes in coverage through adsorption or desorption. The superstructures exhibit a complex pattern of molecules in different geometries.