Left panel: a schematic showing how a di-interstitial forms when a “Y” of four water molecules (red dots) is replaced by a hexagon. Note that this replacement entails formation of three water molecule pentagons and three heptagons. Middle panel: With H, O and Pt atoms represented by small, medium and large balls, the water structure on Pt(111) proposed in Ref. 9. As seen in the side view, browner O atoms lie closer to the metal; yellower lie higher. Green arrows mark the short H-bonds, which are the main focus of this article. The black parallelogram delimits the unit supercell. Right panel: With the same labeling and color scheme, the saturated monolayer, and as indicated, a second-layer water molecule at a favorable binding site.
Infrared absorption spectra (IRAS) for water films adsorbed on Pt(111). All the spectra have peaks at 1965 cm−1 (or 1469 cm−1 for D2O) that are characteristic of the short O–O bonds in both the and layers. (a) For H2O deposited at 152 K, the 0.6 ML (red line) and 1.0 ML (black line) films exhibited the structure in LEED. For H2O deposited at 159 K, a saturated monolayer with the structure is formed in equilibrium with a small amount of crystalline ice (1.2 ML, green line). The spectrum for 1 ML D2O with the frequency multiplied by 1.33 (blue line) is similar to the H2O spectra. (b) Spectrum for 1 ML D2O deposited at 152 K.
IRAS spectra for 1 ML H2O grown at 152 K (black line) and 40 ML crystalline ice grown at 145 K (blue line), both on Pt(111). The crystalline ice spectrum has been multiplied by 0.01 and 0.1 for comparison. The red line shows the nominal location of combination bands for the 1 ML spectrum (see text for discussion).
(a) IRAS spectra for 1 ML H2O deposited at 45 K on Pt(111) and then annealed to the temperatures indicated in the figure. The peak at 1965 cm−1 and the structure within the OH-stretch region (3200 – 3600 cm−1) both develop as the annealing temperature increases. (b) Integrated band intensities for the OH-stretch region and 1965 cm−1 peak (1800 – 2100 cm−1). As the films are annealed to higher temperatures, integrated intensity of the peak at 1965 cm−1 increases whereas the OH-stretch is independent of temperature.
IRAS spectra for water films deposited at 130 K for several coverages. For these conditions, the water films wet the Pt(111) even for θ > 1 ML. The spectra are the average of 1000 scans for a single film for each coverage, with the spectrometer resolution set to 8 cm−1. The peak at 1965 cm−1 disappears by the time θ = 2 ML.
Theoretical and experimental vibrational spectra for several H2O films on Pt(111). For the and layers, the vibrational densities of states were computed at point, then weighted by the Born effective charge squared (see text) and Gaussian-broadened by 35 cm−1.
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