A LEED investigation of clean and oxygen covered Rh(100)

Oed, W.; Dötsch, B.; Hammer, Lutz; Heinz, K.; Müller, K.

doi:10.1016/0039-6028(88)90246-4

Cited by 123 publications

(60 citation statements)

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“…The difference between our DFT-LDA results for the surface relaxation (∆d 12 /d 0 = −3.0 %) and the previous LEED analyses [6,7,8] is decreased significantly compared to the results of Ref. [1,29] (see Table I); the DFT-GGA calculations give a result (∆d 12 /d 0 = −2.8 %) which is even closer.…”

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confidence: 49%

“…Such a study is desirable since all previous DFT calculations [1,2,3,4,5] were performed with the LDA which does not describe the magnetic state reliably; furthermore, in all previous work zero-point and thermal vibrations were ignored, while the LEED data were taken at room temperature [6,7,8]. We will show that the above noted discrepancy between theoretical and measured results is mostly due to the unjustified neglect of vibrational contributions to the free energy.…”

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confidence: 96%

“…Bs, 75.30.Pd, 68.35.Ja, 63.20.Ry The significant discrepancy between first-principles calculations [1,2,3,4,5] and low-energy electron diffraction (LEED) analyses [6,7,8] for the relaxation of the (001) surface of rhodium has been a puzzle for some years. The earlier LEED studies [6,7] concluded that the interlayer spacing of the surface layer (d 12 ) is nearly identical to that in the bulk (d 0 ), i.e., the top-layer relaxation was determined to be ∆d 12 /d 0 = +0.5 ± 1.0 %. A recent LEED study [8] found ∆d 12 /d 0 = −1.16 ± 1.6 %.…”

mentioning

confidence: 99%

“…The earlier LEED studies [6,7] concluded that the interlayer spacing of the surface layer (d 12 ) is nearly identical to that in the bulk (d 0 ), i.e., the top-layer relaxation was determined to be ∆d 12 /d 0 = +0.5 ± 1.0 %. A recent LEED study [8] found ∆d 12 /d 0 = −1.16 ± 1.6 %.…”

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Surface Relaxation and Ferromagnetism of Rh(001)

Cho

Scheffler

1997

Phys. Rev. Lett.

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The significant discrepancy between first-principles calculations and experimental analyses for the relaxation of the (001) surface of rhodium has been a puzzle for some years. In this paper we present density functional theory calculations using the local-density approximation and the generalized gradient approximation of the exchange-correlation functional. We investigate the thermal expansion of the surface and the possibility of surface magnetism. The results throw light on several, hitherto overlooked, aspects of metal surfaces. We find, that, when the free energy is considered, density-functional theory provides results in good agreement with experiments.PACS numbers: 68.35. Bs, 75.30.Pd, 68.35.Ja, 63.20.Ry The significant discrepancy between first-principles calculations [1,2,3,4,5] and low-energy electron diffraction (LEED) analyses [6,7,8] for the relaxation of the (001) surface of rhodium has been a puzzle for some years. The earlier LEED studies [6,7] concluded that the interlayer spacing of the surface layer (d 12 ) is nearly identical to that in the bulk (d 0 ), i.e., the top-layer relaxation was determined to be ∆d 12 /d 0 = +0.5 ± 1.0 %. A recent LEED study [8] found ∆d 12 /d 0 = −1.16 ± 1.6 %. On the other hand, first-principles calculations showed a large top-layer relaxation ranging from −3.2 % to −5.1 %, depending on the calculational scheme and/or the employed numerical accuracy [1,2,3,4,5]. Inward relaxations are indeed the expected behavior of transition metals surfaces (see e.g. Ref.[2] ), and the practical zero relaxation determined by LEED is at least unexpected.In order to reconcile this disagreement between their calculations and experiment, Feibelman and Hamann [1] proposed that in the experimental study the metal surface may be contaminated by residual hydrogen adsorption (see also Ref. [9]). Indeed, hydrogen is not easy to detect and quite soluble in transition metals, such as Ru, Rh, and Pd. Furthermore it is known that adsorbed hydrogen significantly reduces the inward relaxations at metal surfaces as it increases the bond coordination of the surface atoms, making them, to some extent, more bulk like. However, the possibility of hydrogen contamination was strongly rejected by later experimental papers (e.g. [8,10]).Morrison et al.[3] investigated an alternative possibility [11], namely that the presence of surface magnetism could increase the first interlayer spacing, i.e., reducing the large inward relaxation they had obtained in their non-magnetic calculation by "magnetic pressure". In fact, bulk Rh is already close to fulfilling the Stoner criterion of ferromagnetism, and the narrower density of d-states at the surface might stabilize a magnetic state at the surface. Density-functional theory (DFT) together with the local-density-approximation (LDA) gives a nonmagnetic ground state for Rh (001), but this might be due to the LDA. For example, for bulk iron, which is studied in greater detail, the LDA falsely puts the bcc magnetic ground state at a higher energy than the nonma...

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Surface Relaxation and Ferromagnetism of Rh(001)

Cho

Scheffler

1997

Phys. Rev. Lett.

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“…15 Baraldi et al, 16 investigating the reaction between CO and preadsorbed oxygen on Rh͑100͒, observed a higher reactivity for the reconstructed (2ϫ2)p4g O-structure ( O ϭ0.50 ML͒ than for the p(2ϫ2)-O structure ( O ϭ0.25 ML͒. 32 The lower reactivity of the latter was explained by reduced mobility of CO, preventing it to overcome the barrier imposed by CO-O repulsion.…”

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confidence: 99%

Structure sensitivity in the CO oxidation on rhodium: Effect of adsorbate coverages on oxidation kinetics on Rh(100) and Rh(111)

Hopstaken

Niemantsverdriet

2000

The Journal of Chemical Physics

112

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Temperature-programmed reaction spectroscopy has been used to study the surface reaction between CO and O-atoms on Rh͑100͒ and Rh͑111͒ at a range of different adsorbate coverages. Comparison of the reaction on both surfaces in the low coverage regime, where the kinetics can be described by a straightforward Langmuir-Hinshelwood mechanism reveals that the CO oxidation is structure sensitive, with the rate constant being an order of magnitude higher on the Rh͑100͒ than on the Rh͑111͒ surface. As a consequence, the selectivity of the COϩO reaction to CO 2 is about 100% on Rh͑100͒, whereas on Rh͑111͒ the oxidation reaction competes with CO desorption. At low CO coverage, CO oxidation is an elementary step on Rh͑100͒ for a broad range of oxygen coverages. We report kinetic parameters E a ϭ103Ϯ5 kJ/mol and ϭ10 12.7Ϯ0.7 for O ϭ CO →0 on Rh͑100͒. The activation energy for CO oxidation on Rh͑100͒ decreases continuously with increasing O-coverage. At low coverage ( O Ͻ0.25 ML͒ we attribute this to destabilization of CO, leading to an increase in the CO 2 formation rate. At higher coverage ( O Ͼ0.25 ML͒ O-atoms become destabilized as well, as lateral interactions between O-atoms come into play at these coverages. The interactions result in a greatly enhanced rate of reaction at higher coverages.

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Crystal Surfaces

Hove

2006

Materials Science and Technology

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A LEED investigation of clean and oxygen covered Rh(100)

Cited by 123 publications

References 13 publications

Surface Relaxation and Ferromagnetism of Rh(001)

Surface Relaxation and Ferromagnetism of Rh(001)

Structure sensitivity in the CO oxidation on rhodium: Effect of adsorbate coverages on oxidation kinetics on Rh(100) and Rh(111)

Crystal Surfaces

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