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Peter J Feibelman

Publications and source records attributed to Peter J Feibelman.

8 recordsLinked to original sources
PubMed2006

Two-dimensional Ir cluster lattice on a graphene moiré on Ir(111).

Lattices of Ir clusters have been grown by vapor phase deposition on graphene moirés on Ir(111). The clusters are highly ordered, and spatially and thermally stable below 500 K. Their narrow size distribution is tunable from 4 to about 130 atoms. A model for cluster binding to the graphene is presented based on scanning tunneling microscopy and density functional theory. The proposed binding mechanism suggests that similar cluster lattices might be grown of materials other than Ir.

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PubMed2006

Lubrication theory of drag on a scanning probe in structured water, near a hydrophilic surface.

The drag is evaluated, in lubrication theory, on a parabolic-cylindrical tip moving parallel to a flat sample, in water, close enough that the presumed nanometer-thick, structured-water, "interphase" coatings of both it and the sample overlap. Assuming coatings of width, w, and of viscosity, eta, much larger than bulk water's, the friction force is predicted to equal -2pietacRphi(D/2w), where R is the tip's radius of curvature, c is its speed, D is the tip-sample separation, and Phi is a universal function whose value only differs noticeably from ln(2w/D) for D < w.

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PubMed2004

Experimental evidence for a partially dissociated water bilayer on Ru[0001].

Core-level photoelectron spectra, in excellent agreement with ab initio calculations, confirm that the stable wetting layer of water on Ru[0001] contains O-H and H2O in roughly 3:5 proportion, for OHx coverages between 0.25 and 0.7 ML, and T<170 K. Proton disorder explains why the wetting structure looks to low energy electron diffraction (LEED) to be an ordered p(square root of 3 x square root of 3)R30 degrees adlayer, even though approximately 3/8 of its molecules are dissociated. Complete dissociation to atomic oxygen starts near 190 K. Low photon flux in the synchrotron experiments ensured that the diagnosis of the nature of the wetting structure quantified by LEED is free of beam-induced damage.

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PubMed2004

Novel water overlayer growth on Pd(111) characterized with scanning tunneling microscopy and density functional theory.

Scanning tunneling microscopy (STM) images of water submonolayers on Pd(111) reveal quasiperiodic and isolated adclusters with internal structure that would ordinarily be ascribed to icelike puckered hexagonal units. However, density functional theory and STM simulations contradict this conventional picture, showing instead that the water adlayers are composed mainly of flat-lying molecules arranged in planar water hexagons. A new rule for two dimensional (2D) water growth is offered that generates the structures observed experimentally from planar hexamer units.

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PubMed2004

Effect of high-viscosity interphases on drainage between hydrophilic surfaces.

Drainage of water from the region between an advancing probe tip and a flat sample is reconsidered under the assumption that the tip and sample surfaces are both coated by a thin water "interphase" (of width approximately a few nanometers) whose viscosity is much higher than that of the bulk liquid. A formula derived by solving the Navier-Stokes equations allows one to extract an interphase viscosity of approximately 59 kPa x s (or approximately 6.6 x 10(7) times the viscosity of bulk water at 25 degrees C) from interfacial force microscope measurements with both tip and sample functionalized hydrophilic by OH-terminated tri(ethylene glycol) undecylthiol, self-assambled monolayers.

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PubMed2003

Reactive wetting: H2O/Rh(111).

First-principles calculations imply that neither H2O bilayers nor half-dissociated, H2O+OH+H monolayers are thermodynamically stable on clean Rh(111). Thus, the experimental observation that Rh(111) supports a periodic 2D water adlayer needs an explanation. Chemistry involving common surface impurities, notably C atoms, may be the answer. Calculations show they provide favorable binding sites for H atoms detached from H2O. The resulting OH fragments can anchor a 2D water layer to the surface.

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PubMed2002

Partial dissociation of water on Ru(0001).

Initial water deposition on the moderately reactive precious metal surface Ru(0001) has been thought to produce an ice-like bilayer. However, calculations from first principles show that the wetting layer observed on Ru(0001) cannot be formed of undissociated water molecules. An energetically favorable alternative, consistent with the remarkable observation that the wetting layer's oxygen atoms are nearly coplanar, is a half-dissociated monolayer wherein water molecules and hydroxyl fragments are hydrogen-bonded in a hexagonal structure and hydrogen atoms bind directly to the metal.

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