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M. Meier, J. Hulva, Z. Jakub, J. Pavelec, M. Setvin, R. Bliem, M. Schmid, U. Diebold, C. Franchini, G. Parkinson:
"Water agglomerates on Fe_{3}O_{4}(001)";
Proceedings of the National Academy Sciences USA, 115 (2018), E5642 - E5650.

Determining the structure of water adsorbed on solid surfaces is a
notoriously difficult task and pushes the limits of experimental
and theoretical techniques. Here, we follow the evolution of water
agglomerates on Fe3O4(001); a complex mineral surface relevant in
both modern technology and the natural environment. Strong
OH-H2O bonds drive the formation of partially dissociated water
dimers at low coverage, but a surface reconstruction restricts the
density of such species to one per unit cell. The dimers act as an
anchor for further water molecules as the coverage increases,
leading first to partially dissociated water trimers, and then to a
ring-like, hydrogen-bonded network that covers the entire surface.
Unraveling this complexity requires the concerted application
of several state-of-the-art methods. Quantitative temperatureprogrammed
desorption (TPD) reveals the coverage of stable structures,
monochromatic X-ray photoelectron spectroscopy (XPS) shows
the extent of partial dissociation, and noncontact atomic force
microscopy (AFM) using a CO-functionalized tip provides a direct
view of the agglomerate structure. Together, these data provide
a stringent test of the minimum-energy configurations determined
via a van der Waals density functional theory (DFT)-based
genetic search.