Driving Force Behind the O-Rh(001) Clock Reconstruction

A novel rhombi-chain network is derived from low energy electron diffraction experimental observations and the recent model theory, revealing that the O-Rh(100) clock-rotation is driven by an electrostatic force arisen from bond formation. Thus the O-Rh bond suffers from tension other than compression, or strain relief. As O -1 evolves into the hybridized- O -2,a Rh 5 O cluster in the c(2 × 2) phase develops into a Rh 4 O tetrahedron and yields the overall (2 × 2)p4g reconstruction. In the (2 × 2)p4g phase, the hollow-sited O -2 defines one Rh + ion and two lone-pair-induced Rh dipoles of its four surface neighbors. The surface atomic ratio (O : Rh = 1 : 2) allocates, therefore, half of the surface Rh atoms to be the Rh dipoles and another half to play dual roles of Rh + ion and Rh dipole. Interactions along the "dipole–dipole – Rh +/dipole – Rh +/dipole" strings create the rhombi-chain at the <11> directions, and a responding bond tension confines the (2 × 2)p4g clock rotation.

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Interaction of Hydrogen on a Lanthanum hexaboride 111 Surface

The Journal of Undergraduate Research at the University of Illinois at Chicago ◽

10.5210/jur.v3i1.7472 ◽

2009 ◽

Vol 3 (1) ◽

Author(s):

J. Cameli ◽

A. Tillekaratne ◽

M. Trenary

Keyword(s):

Photoelectron Spectroscopy ◽

Alternative Energy ◽

Bond Formation ◽

Lanthanum Hexaboride ◽

Current Level ◽

X Ray ◽

Low Energy Electron Diffraction ◽

Reflection Absorption Infrared Spectroscopy ◽

Low Energy Electron ◽

Lower Temperature

In order to sustain society's current level of energy consumption and prevent irreversible climate degradation due to the greenhouse effect an alternative energy carrier is required. The aim of this experiment was to determine the conditions under which a lanthanum hexaboride (LaB6) surface would form boron-hydrogen (B-H) bonds when exposed to hydrogen. Reflection absorption infrared spectroscopy (RAIRS) was used to confirm formation of bonds and X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) were used to characterize the surface. Upon completion of the experiment no B-H bonds were found to form under the conditions tested. However, it is believed that the bond formation may have been impeded by tungsten contamination of the surface or may have been due to the instability of the B-H bond. A lower temperature could be required for their formation.

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THE sp HYBRID BONDING OF C, N AND O TO THE fcc(001) SURFACE OF NICKEL AND RHODIUM

Surface Review and Letters ◽

10.1142/s0218625x00000361 ◽

2000 ◽

Vol 07 (03) ◽

pp. 347-363 ◽

Cited By ~ 22

Author(s):

CHANG Q. SUN

Keyword(s):

Driving Force ◽

Electrostatic Force ◽

Bond Formation ◽

Technical Innovation ◽

Hollow Site ◽

Strong Bond ◽

Orbital Hybridization ◽

Host Atom ◽

Initial Stage ◽

Valence Electrons

This brief review focuses on the nature, kinetics, dynamics and consequences of the sp-orbital hybrid bonding of C, N and O to the Ni/Rh(001) surfaces which give rise to the same kind of "radial and then the p4g clock" reconstruction. It is identified that the "radial" and the subsequent "clock" reconstruction result from the adsorbate–substrate bond formation with sp-orbital hybridization, and that the driving force behind the reconstruction originates from the electrostatic interaction along the <11> direction. At the initial stage, A-1 (A=C, N or O adsorbate) sinks into the fourfold hollow site and forms one bond with a B (B = Ni or Rh host atom) underneath, giving rise to an AB5 cluster with four dipoles at the surface. As A-1 evolves into the hybridized-A-n (n=4, 3, 2), the AB5 cluster evolves into an AB4 tetrahedron. Meanwhile, the AB4 tetrahedron redefines three of the four surface dipoles as B+, B2+, B+/ dipole or Bdipole, depending on the valence value of the adsorbate. The electrostatic force arises upon repopulating the valence electrons, which creates rhombus strings along the <11> direction. With the presence of nonbonding lone pairs, the clock rotation on Ni(00l)-(2×2)p4g-2N-3 and Rh(00l)-(2×2)p4g-2O-2 surfaces is initiated by the alternate attraction and repulsion in the <11> direction and the rotation is stabilized by bond tension; whereas the clock rotation on the Ni(00l)-(2×2)p4g-2C-4 surface is driven by the nonequivalent electrostatic repulsion in the <11> direction and the rotation is balanced by strong bond compression. The findings so far have led to technical innovation for the adhesion between diamond and metals by designing a gradient TiCN transition layer to neutralize the bond stress.

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Low-Energy-Electron-Diffraction Structural Studies of (100) Cleavage Surfaces of In4Se3 Layered Crystals

Ukrainian Journal of Physics ◽

10.15407/ujpe59.06.0612 ◽

2014 ◽

Vol 59 (6) ◽

pp. 612-621 ◽

Cited By ~ 1

Author(s):

P.V. Galiy ◽

◽

Ya.B. Losovyj ◽

T.M. Nenchuk ◽

I.R. Yarovets’ ◽

...

Keyword(s):

Electron Diffraction ◽

Low Energy ◽

Energy Electron ◽

Structural Studies ◽

Low Energy Electron Diffraction ◽

Layered Crystals ◽

Low Energy Electron

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Oblique-incidence Reflectivity Difference (OI-RD) and Leed Studies of Adsorption and Growth of Xe on Nb(110)

MRS Proceedings ◽

10.1557/proc-780-y3.11 ◽

2003 ◽

Vol 780 ◽

Author(s):

P. Thomas ◽

E. Nabighian ◽

M.C. Bartelt ◽

C.Y. Fong ◽

X.D. Zhu

Keyword(s):

Transition Layer ◽

Layer Growth ◽

Flow Mode ◽

Layer By Layer ◽

Zeroth Order ◽

Step Flow ◽

Low Energy Electron Diffraction ◽

Oriented Film ◽

Low Energy Electron

AbstractWe studied adsorption, growth and desorption of Xe on Nb(110) using an in-situ obliqueincidence reflectivity difference (OI-RD) technique and low energy electron diffraction (LEED) from 32 K to 100 K. The results show that Xe grows a (111)-oriented film after a transition layer is formed on Nb(110). The transition layer consists of three layers. The first two layers are disordered with Xe-Xe separation significantly larger than the bulk value. The third monolayer forms a close packed (111) structure on top of the tensile-strained double layer and serves as a template for subsequent homoepitaxy. The adsorption of the first and the second layers are zeroth order with sticking coefficient close to one. Growth of the Xe(111) film on the transition layer proceeds in a step flow mode from 54K to 40K. At 40K, an incomplete layer-by-layer growth is observed while below 35K the growth proceeds in a multilayer mode.

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