Adsorbate induced relaxations of S/Ru(0001): p(2 × 2) and p(√3 × √3)R30° structures

Jürgens, D.; Held, Georg; Pfnür, H.

doi:10.1016/0039-6028(94)90621-1

Cited by 46 publications

(18 citation statements)

References 23 publications

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“…The Ru-S bond length in the relaxed structure is 2.32 Å, and the S adatom is about 1.602 Å (d S-Ru ) above the surface Ru layer. Both values are in good agreement with experimental values (bond length of 2.28 Å and interlayer spacing of 1.605 Å) obtained from the ordered p(2 Â 2)-S phase on Ru(0 0 0 1) [26]. The spacing between the first and the second Ru layer (d Ru1-Ru2 ) and the rumpling D \ of the first Ru layer are also fairly close to the experimental values of 2.115 Å and 0.03 Å, respectively.…”

Section: Introductionsupporting

confidence: 86%

“…Jakob et al reported that Pt adatoms occupy both H and F sites on Ru(0 0 0 1), and form two types of island with different orientations [25]. For sulfur adsorption on Ru(0 0 0 1), a p(2 Â 2)-S superstructure was observed [26]. Diffusion of metal adatoms on some transition metal surfaces were investigated by using scanning tunneling microscopy (STM) or field ion microscopy (FIM), and the following diffusion barriers were obtained, 0.16 eV for the Ag/Pt(1 1 1) system [27] and 0.097 eV for the Ag/Ag(1 1 1) system [28].…”

Section: Introductionmentioning

confidence: 96%

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Adsorption and diffusion of adatoms on Ru(0001): A first-principles study

Sun

Jia

et al. 2008

Surface Science

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Section: Introductionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 96%

Adsorption and diffusion of adatoms on Ru(0001): A first-principles study

Sun

Jia

et al. 2008

Surface Science

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“…These efforts have included work on close-packed surfaces of transition (Co(0 0 0 1) [9], Ru(0 0 0 1) [27][28][29][30], Ir(1 1 1) [31], Ni(1 1 1) [32][33][34][35], Pd(1 1 1) [36][37][38][39][40], Pt(1 1 1) [41][42][43][44], Rh(1 1 1) [45][46][47]) and noble metals (Ag(1 1 1) [12,48,49], Au(1 1 1) [50][51][52], Cu(1 1 1) [53][54][55]). The formation of ( p 3 Â p 3) R30°structure on the (1 1 1) surfaces was frequently observed while the (2 Â 2) structure was commonly reported on the (0 0 0 1) face.…”

Section: Introductionmentioning

confidence: 99%

First-principles studies of H2S adsorption and dissociation on metal surfaces

2008

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Exposure of Pd-based hydrogen purification membranes to H,S. a common contaminant in coal gasification streams, can cause membrane performance to deteriorate, either by deactivating surface sites required for dissociative H, adsorption or by forming a low-permeability sulfide scale. In this work. the composition, structure, and catalytic activity of Pd4S, a surface scale commonly observed in Pd-membrane separation of hydrogen from sulfur-containing gas streams, were examined using a combination of experimental characterization and density functional theory (DFT) calculations. A Pd,S sample was prepared by exposing a 100 f1m Pd foil to H2S at 908 K. Both X-ray photoemission depth profiling and low energy ion scattering spectroscopic (LEISS) analysis reveal slight sulfur-enrichment of the top surface of the sample. This view is consistent with the predictions of DFT atomistic thermodynamic calculations. which identified S-terminated Pd,S surfaces as energetically favored over corresponding Pd-terminated surfaces. Activation barriers for H2 dissociation on the Pd,S surfaces were calculated. Although barriers are higher than on Pd(lll). transition state theory analysis identified reaction pathways on the S-terminated surfaces for which hydrogen dissociation rates are high enough to sustain the separation process at conditions relevant to gasification applications.

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“…The experimental setup was described previously. 5 The main experimental results are obtained by measuring LEED spot profiles with a three-grid backview LEED optics and a charge-coupled device ͑CCD͒ camera. The following other methods were used: contact potential difference ͑CPD͒ monitored by a small three-electrode electron gun for coverage calibration, mass spectrometry with a quadrupole mass spectrometer, Auger electron spectroscopy using a cylindrical mirror analyzer for testing cleanness of adsorbate and substrate, and a high resolution spot profile analysis ͑SPA͒ LEED instrument for examining the structure of the substrate surface.…”

Section: Methodsmentioning

confidence: 99%

Phase transitions in the adsorption system Li/Mo(112)

et al. 2000

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Experimental studies of the phase transitions in the adsorption system Li/Mo͑112͒ are presented. This system is a model system for highly anisotropic interactions. From measurements of the half-widths of the low-energy electron diffraction spot profiles a phase diagram is derived for the whole submonolayer region of coverage in the temperature range 100-500 K. The commensurate low-coverage phases below ϭ0.6 form chains normal to the troughs of the substrate. The commensurate p(4ϫ1) phase, which is completed at a coverage, , of 0.25 monolayers ͑ML͒, seems to be truly long range ordered, whereas the p(2ϫ1) phase at ϭ0.5 still contains domain boundaries even at the lowest temperature of 100 K. Both undergo temperaturedriven order-disorder phase transitions. In contrast, the incommensurate phases existing in the coverage range ϭ0.66-0.90 form chains along the troughs, which are only weakly coupled normal to the troughs of the substrate. These phases exhibit two coverage-driven phase transitions from rectangular to oblique units cells and back at critical coverages of 0.66 and 0.85, respectively, and represent floating solids. As a function of temperature, they undergo a two-dimensional melting transition. Close to the critical coverages, the melting temperatures show a sharp drop below the temperature range accessible in our experiments. Both functional dependences of the angular deviation from 90°and of the melting temperature on coverage are in good agreement with a phenomenological theoretical model, assuming an instability of the shear modulus of the adsorbate unit cell at the critical coverages.

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Adsorbate induced relaxations of S/Ru(0001): p(2 × 2) and p(√3 × √3)R30° structures

Cited by 46 publications

References 23 publications

Adsorption and diffusion of adatoms on Ru(0001): A first-principles study

Adsorption and diffusion of adatoms on Ru(0001): A first-principles study

First-principles studies of H2S adsorption and dissociation on metal surfaces

Phase transitions in the adsorption system Li/Mo(112)

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