The Pt(110) phase transitions: A study by rutherford backscattering, nuclear microanalysis, LEED and thermal desorption spectroscopy

Jackman, T. E.; Davies, John; Jackson, O.P.; Unertl, W. N.; Norton, P. R.

doi:10.1016/0039-6028(82)90158-3

Cited by 161 publications

(54 citation statements)

References 33 publications

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“…Most other models could be excluded by ion scattering studies [7][8][9][10][11]. The surface corrugation of the missing row model is also consistent with the results of a helium scattering L656 W. Moritz,D.…”

supporting

confidence: 73%

“…The missing row model is consistent with the results of most other methods applied to the (110) faces of Pt, Ir and Au. All three faces are believed to exhibit the same reconstruction [3][4][5][6][7][8][9][10][11].…”

mentioning

confidence: 99%

“…For Pt(ll0) two possible values were found for the top layer spacing and the authors favored an expansion [5]. With ion-scattering [7][8][9][10][11] no clear distinction between expansion or contraction for the first layer spacing could be made but the value of 0.08 ,~ for the lateral pairing displacement in the second layer found recently [11] agrees within the error limits with the X-ray data [1] where a shift of 0.12 ~, has been found. A recent low energy ion scattering study [9] results in a contraction of 15-23% of the top layer spacing and also indicates a lateral shift of the atomic positions in the second layer.…”

mentioning

confidence: 99%

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Multilayer distortion in the reconstructed (110) surface of Au

1985

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A new LEED intensity analysis of the reconstructed Au(110)-(1×2) surface results in a modification of the missing row model with considerable distortions which are at least three layers deep. The top layer spacing is contracted by about 20%, the second layer exhibits a lateral pairing displacement of 0.07 .~ and the third layer is buckled by 0.24 ,~. Distortions in deeper layers seem to be probable but have not been considered in this analysis. The inter-atomic distances in the distorted surface region show both an expansion and a contraction compared to the bulk value and range from 5% contraction to about 4% expansion.

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supporting

confidence: 73%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Multilayer distortion in the reconstructed (110) surface of Au

1985

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“…7 This means that, above the site-switching point, the surface is mostly covered by CO͑a͒, close to 0.5 monolayer, except for a limited number of remaining ͑1ϫ2͒ domains. Oxygen dissociation hardly takes place on the ͑1ϫ1͒ plane stabilized by CO͑a͒.…”

Section: Co 2 Formation On "1ã1…mentioning

confidence: 99%

“…7 These two structures yield differently oriented oxygen adsorption sites, emitting product CO 2 into different directions. The ͑1ϫ2͒ reconstructed surface consists of three-atom-wide ͑111͒ terraces declining about 30°into the ͓001͔ direction.…”

Section: Introductionmentioning

confidence: 99%

CO 2 desorption dynamics on specified sites and surface phase transitions of Pt(110) in steady-state CO oxidation

Rzeznicka

Moula

Garza

et al. 2003

The Journal of Chemical Physics

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The spatial and velocity distributions of desorbing product CO 2 were studied in the steady-state CO oxidation on Pt͑110͒ by cross-correlation time-of-flight techniques. The surface structure transformation was monitored by LEED in the course of the catalyzed reaction. In the active region, where the surface was highly reconstructed into the missing-row form, CO 2 desorption split into two directional lobes collimated along 25°from the surface normal in the plane including the ͓001͔ direction, indicating the CO 2 formation on inclined ͑111͒ terraces. The translational temperature was maximized at the collimation angle, reaching about 1900 K. On the other hand, CO 2 desorption sharply collimated along the surface normal at CO pressures where ͑1ϫ2͒ domains disappeared. The distribution change from an inclined desorption to a normally directed one was abrupt at the CO pressure where the half-order LEED spot already disappeared. This switching point was more sensitive than LEED towards the complete transformation from ͑1ϫ2͒ to ͑1ϫ1͒ and was then used to construct a surface phase diagram for working reaction sites in the pressure range from 1ϫ10 Ϫ7 Torr to 1ϫ10 Ϫ4 Torr of oxygen. The turnover frequency of CO 2 formation was enhanced on ͑1ϫ2͒ domains with increasing CO pressure.

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Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

Ertl

2008

Handbook of Heterogeneous Catalysis

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The rate of a catalytic reaction is governed by the underlying mechanism, i.e. the sequence of elementary reaction steps, and depends on the external control parameters such as the concentrations (= partial pressures) p j of educt and product species and temperature T, if transport processes are excluded in this context. More specifically, usually the adsorbed species are assumed to be randomly distributed over the surface, and their concentrations (= coverages) θ i are described within a mean-field approximation so that the reaction rate (= number of molecules r formed per unit time, dn r /dt t ) is given by dn r dt = f θ i , T ( ) (1) whereby the coverages θ i are in turn determined by a set of differential equations (modeling the individual steps of adsorption, desorption and surface reaction) of the typeProper treatment then requires that additional constraints given by heat and mass balance are taken into consideration.Under flow conditions with the external control parameters being kept fixed, usually the reaction proceeds at steady state with constant rate, i.e., dn r /dt = constant and dθ i /dt = 0. Due to the nonlinear character of the quoted differential equations, this has, however, not necessarily to be the case; the kinetics may -for certain ranges of parameters -become oscillatory or even irregular (chaotic). Such systems are typically far away from equilibrium, and (i) By far the most detailed insights into the underlying mechanisms and the general phenomenology of spatio-temporal self-organization were obtained in studies with well-defined single crystal surfaces by applying the arsenal of modern surface physical methods.(ii) Single crystal studies are usually conducted with bulk samples under low pressure conditions (≤ 10 -4 mbar)where the temperature changes associated with varying reaction rate are negligible. In addition, the mean-free path of gaseous molecules is comparable or even larger than the dimensions of the reaction vessel, which is operated as a continuous flow reactor. Hence, concentration gradients in the gas phase are practically instantaneously (≤ 10 -3 s)transmitted. Analysis of such experiments is thus appreciably simplified.(iii) Experiments with polycrystalline, i.e. "real", catalysts are usually conducted at elevated partial pressures (≥ 1 mbar) under which the heat released by the reaction may lead to noticeable temperature variations. The resulting thermokinetic effects may become dominating, so that even the nonuniformity of the surface chemistry is masked and quite novel phenomena may arise. Ideally, the reaction is conducted in a way, which may be described by a continuously stirred tank reactor (CSTR), i.e., perfect mixing ensures that the concentrations are everywhere identical.However, frequently a concentration profile exists along the reactor, which is hence rather of the plug-flow type. It is thus evident that heat and mass transfer limitations may play important roles with such systems.Generally, an extended system such as a single crystal surface, or even more ...

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The Pt(110) phase transitions: A study by rutherford backscattering, nuclear microanalysis, LEED and thermal desorption spectroscopy

Cited by 161 publications

References 33 publications

Multilayer distortion in the reconstructed (110) surface of Au

Multilayer distortion in the reconstructed (110) surface of Au

CO 2 desorption dynamics on specified sites and surface phase transitions of Pt(110) in steady-state CO oxidation

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

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