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Interpretation of high-resolution images of the best-bound wetting layers on Pt(111)
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10.1063/1.3488803
/content/aip/journal/jcp/133/15/10.1063/1.3488803
http://aip.metastore.ingenta.com/content/aip/journal/jcp/133/15/10.1063/1.3488803

Figures

Image of FIG. 1.
FIG. 1.

After Ref. 10, raw STM data from a superlattice of water molecules in a single layer on Pt(111).

Image of FIG. 2.
FIG. 2.

(a) Removing the Y formed by four water molecules represented by red dots (upper panel) produces the triangular vacancy island of the center panel. Replacing them with six water molecules disposed hexagonally (lower panel) amounts to creating a di-interstitial. Three pentagon-heptagon pairs then surround the hexagon, as indicated. (b) Top and side views of a , DFT-optimized water adlayer on Pt(111), with a di-interstitial in each unit supercell. Large, medium, and small spheres represent Pt, O, and H atoms. O atoms are color-coded according to height, darker corresponding to lower and lighter to higher. The darkest, in atop sites, are just 2.2 Å above Pt atoms.

Image of FIG. 3.
FIG. 3.

Top and side views of a DFT-optimized water adlayer on Pt(111), with a di-interstitial, and a second-layer molecule in each unit supercell. Large, medium, and small spheres represent Pt, O, and H atoms. O atoms are color-coded according to height, darker corresponding to lower and lighter to higher.

Image of FIG. 4.
FIG. 4.

Top view of a DFT-optimized water adlayer on Pt(111), with a vacancy island in each unit supercell. Large, medium, and small spheres are Pt, O, and H atoms. O atoms are color-coded according to height, with darker corresponding to lower and lighter to higher. An OH- pair (highlighted by an ellipse) has formed in the course of optimization. The O atom of its OH is less than 2.1 Å above a Pt. In the cell delimited by the parallelogram, the O atoms of two flat-lying ’s in atop sites are somewhat less than 2.2 Å above Pt atoms. That of a third lies at a height of 2.6 Å.

Image of FIG. 5.
FIG. 5.

Top view of a DFT-optimized, water adlayer on Pt(111), rebonded, relative to Fig. 4, so as (note the circled molecules) to reduce the number of dangling H atoms at the vacancy island periphery. Large, medium, and small spheres are Pt, O, and H atoms. O atoms are color-coded according to height, with darker corresponding to lower and lighter to higher. Again, an OH- pair has formed in the course of optimization.

Image of FIG. 6.
FIG. 6.

Side and top views of a DFT-optimized version of Ref. 11’s vacancy-island wetting structure, with large, medium, and small spheres representing Pt, O, and H atoms. The parallelogram delimits the unit supercell. O atoms are browner if lower and yellower if higher. Each of the six molecules labeled “e” at the vacancy edge dangles an H atom into the vacancy. Arrows point to two H-down water molecules, which, in Ref. 11, are H-up and bind a second layer water molecule, absent here. As noted in Table I, adding it actually leads to reduced binding per .

Image of FIG. 7.
FIG. 7.

Top view of a vacancy island wetting structure, alternatively proton-ordered, compared to Fig. 4, for improved binding. The six molecules labeled e at the vacancy island edges would lie low and flat were that energetically preferable. That they do not is evidence that unsatisfied acceptor H-bonds are less costly than unsatisfied donor bonds.

Image of FIG. 8.
FIG. 8.

With large, medium, and small spheres representing Pt, O, and H atoms, top view of DFT-optimized wetting structure, whose vacancy triangle altitudes lie along directions (as indicated by three arrows), instead of the observed directions. The dashed parallelogram delimits the unit supercell. The wetting structure was obtained by reflecting that of Fig. 6 in a plane normal to the surface, through the upper- and lowermost vertices of the parallelogram, specifically, a plane. With O atoms browner if lower, and yellower if higher, notice that seven flat-lying molecules in the cell lie low on the surface, compared to just five in the unreflected wetting structures of Figs. 6 and 7.

Image of FIG. 9.
FIG. 9.

After Ref. 25, Fig. 2, solid curves are digitized copies of the Kr thermal desorption spectra (ramp rate 1 K/s) from bare Pt(111) (“W0”) and from Pt(111) covered by a water monolayer (“W1”) The dashed curves represent W0 shifted down 18.1 K and scaled up by a factor 1.08, and shifted down by 13.7 K, and scaled by the factor 0.06.

Image of FIG. 10.
FIG. 10.

A STM image, and line scan of the edge of a water island. The black region at the right, and the black regions interior to the island, where water is absent, are noticeably darker than the gray triangles, further evidence that the dark triangles are not empty.

Tables

Generic image for table
Table I.

Density functional binding energy (BE) per adsorbed water molecule in various periodic wetting layer arrangements on Pt(111).

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/content/aip/journal/jcp/133/15/10.1063/1.3488803
2010-10-18
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Interpretation of high-resolution images of the best-bound wetting layers on Pt(111)
http://aip.metastore.ingenta.com/content/aip/journal/jcp/133/15/10.1063/1.3488803
10.1063/1.3488803
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