Phase transformations of the H/W(110) and H/Mo(110) surfaces

Altman, Michael S.; Chung, J. W.; Estrup, P. J.; Kosterlitz, J; Prybyla, J. A.; Sahu, D.; Ying, S. C.

doi:10.1116/1.574182

Cited by 56 publications

(24 citation statements)

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“…This scenario can be rejected because the diffusion barrier is as high as 0.31 eV in our study. The superstructure LEED pattern formed by hydrogen atoms on this surface is destroyed above 300 K [14]. This result supports our result that the diffusion barrier is as small as 0.05 eV.…”

Section: Hydrogen Diffusion and Delocalization On W(1 1 0)supporting

confidence: 92%

“…At both h = 0.5 and h = 0.75, the TF site is the most stable. The site conversion proposed by previous experiments was not found [13][14][15]. The relative adsorption energy is slightly different from that for h = 1.0.…”

Section: H Adsorption On the W(1 1 0) Surfacecontrasting

confidence: 57%

“…In previous LEED experiments, two types of superstructure LEED patterns, (2 · 1) and (2 · 2)-3H were observed [14]. Therefore, we studied hydrogen adsorption structures for these two coverage regimes.…”

Section: H Adsorption On the W(1 1 0) Surfacementioning

confidence: 93%

“…With the effective medium theory, Norskov concluded that the adsorption energy difference between long-bridge sites (LB sites) and threefold hollow sites (TF sites) is so small that hydrogen atoms can delocalize within an hourglass region [12]. Low energy electron diffraction (LEED) intensity analysis by Estrup [13,14] and a high resolution X-ray photoelectron spectroscopy study by Citrin [15] concluded that hydrogen atoms occupy LB sites at low coverage and occupy TF sites with increasing coverage. They insisted that the first layer of the W substrate is reconstructed moving toward the 1 1 0 direction.…”

Section: Introductionmentioning

confidence: 98%

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A theoretical study of hydrogen adsorption and diffusion on a W(1 1 0) surface

Nojima

Yamashita

2007

Surface Science

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Section: Hydrogen Diffusion and Delocalization On W(1 1 0)supporting

confidence: 92%

Section: H Adsorption On the W(1 1 0) Surfacecontrasting

confidence: 57%

Section: H Adsorption On the W(1 1 0) Surfacementioning

confidence: 93%

Section: Introductionmentioning

confidence: 98%

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A theoretical study of hydrogen adsorption and diffusion on a W(1 1 0) surface

Nojima

Yamashita

2007

Surface Science

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“…The [110]-offset from the long-bridge position is y H = 0.55 ± 0.01Å. Within the computational error the hydrogen relaxes exactly in the geometric threefold site and there is no theoretical evidence for a pronounced top-layer-shift reconstruction in agreement with the lowenergy electron diffraction experiments [21]. In comparison both bridge positions are clearly energetically unfavorable, and the on-top position is even worse.…”

supporting

confidence: 51%

Frustrated H-Induced Instability of Mo(110)

Köhler¹,

Ruggerone²,

Wilke³

et al. 1995

Phys. Rev. Lett.

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Using helium atom scattering Hulpke and Lüdecke recently observed a giant phonon anomaly for the hydrogen covered W (110) and Mo (110) surfaces. An explanation which is able to account for this and other experiments is still lacking. Below we present density-functional theory calculations of the atomic and electronic structure of the clean and hydrogencovered Mo (110) [3]) are only available for ΓH and ΓS. Thus, we focus our attention particularily on these two directions. For both surfaces two different softenings in the surface phonon branches were observed at the critical wave vectors: a smaller dip and a very deep and sharp indentation fromhω ≈ 15 meV tohω ≈ 2 meV. Only the phonon dispersion curves of quasi-one-dimensional conductors, like KCP [K 2 Pt(CN) 4 Br 3 ] [5] are characterized by similarly deep anomalies strongly localized in reciprocal space. A pronounced but less sharp damping of longitudinal surface phonons was observed for the (100) surfaces of W [6,7] and Mo [8] and was explained in terms of the nested structure of the Fermi surface [9,10]. In the case of W (100) this Fermi surface nesting is apparently so strong that it induces a rebonding at the surface and a structural rearrangement, i.e. a c(2 × 2) surface reconstruction at temperatures below T c ≈ 250 K (for a review see [11]). For the clean (110) surfaces of W and Mo no indication of an anomaly is found, but this only appears when the surfaces are covered with a full layer of hydrogen. Nevertheless, a close link between the surface phonon anomalies and H vibrations seems to be ruled out, since the HAS spectra remain practically unchanged when deuterium is adsorbed instead of hydrogen [2,3].Angular resolved photoemission (ARP) studies have been performed by Kevan and coworkers [12][13][14] for clean and hydrogen covered W (110) and Mo (110). These studies give no evidence of the existence of parallel segments of the Fermi-surface contours separated by wave vectors comparable with the HAS determined critical wave vectors and thus there appeared to be compelling reason for abandoning the nesting mechanism as a possible origin of the anomalies seen in HAS.The situation became even more puzzling when very careful high resolution electron energy loss spectroscopy (HREELS) studies [15] of hydrogen covered W (110) observed the Rayleigh wave phonon branch with the small dip at Q exp c1 exactly as the HAS results. However, the giant anomaly was not detected.At present there exists no explanation which is able to account for the observed two phonon anomalies and is compatible with the different experimental data (HAS, HREELS, and ARP). We therefore performed ab-initio calculations of the surface atomic geometries and the electronic properties of the clean and H-covered Mo (110) surface. The results for the adsorbate covered surface provide clear evidence for a Fermi surface nesting instability at wave vectors which are in remarkable agreement with those at which the phonon anomalies occur for this system [Q . We choose the x-axis along [001] and t...

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3.4.1 Adsorbate properties of hydrogen on solid surfaces

Christmann¹

Adsorbed Layers on Surfaces. Part 5: Adsorption of Molecules on Metal, Semiconductor and Oxide Surfaces

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Phase transformations of the H/W(110) and H/Mo(110) surfaces

Cited by 56 publications

References 0 publications

A theoretical study of hydrogen adsorption and diffusion on a W(1 1 0) surface

A theoretical study of hydrogen adsorption and diffusion on a W(1 1 0) surface

Frustrated H-Induced Instability of Mo(110)

3.4.1 Adsorbate properties of hydrogen on solid surfaces

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