Deuterium dissociation on ordered Sn/Pt(111) surface alloys

203

185

This computational study is motivated by the apparent conflict between an experiment on dissociation of H 2 and D 2 on Pt͑111͒, which suggests a rather corrugated potential energy surface ͑PES͒ for the H 2 /Pt͑111͒ system, and an experiment showing only weak nonzero-order diffraction of HD scattering from Pt͑111͒. In the calculations we have used density functional theory ͑DFT͒ within the generalized gradient approximation ͑GGA͒, including scalar relativistic effects and modelling the Pt͑111͒ surface as a slab. We have found that the H 2 /Pt͑111͒ PES is both energetically and geometrically corrugated. We have also found that there are reaction paths without or with very low barriers leading to dissociation of H 2 on the Pt͑111͒ surface, but that there are other reaction paths with substantial barriers. By performing extensive calculations on H interacting with a Pt͑111͒ surface we have shown that a DFT/GGA approach that includes scalar relativistic effects is capable of describing the interaction between a hydrogen atom and a Pt͑111͒ surface in a way that is, for the most part, consistent with experiments.

Section: B H On Pt"111…supporting

confidence: 74%

Atomic and molecular hydrogen interacting with Pt(111)

Olsen

Kroes

Baerends

1999

203

185

“…Molecular beam results on reaction of D 2 on Pt͑111͒ are available from different groups. 4, 60 Here, we will compare our results with experimental results of Luntz et al 4 for reasons discussed in Ref. 61.…”

Section: E Comparison With Experiment: Reactionmentioning

confidence: 57%

Reactive and diffractive scattering of H2 from Pt(111) studied using a six-dimensional wave packet method

Pijper

Kroes

Olsen

et al. 2002

112

144

We present results of calculations on dissociative and rotationally ͑in͒elastic diffractive scattering of H 2 from Pt͑111͒, treating all six molecular degrees of freedom quantum mechanically. The six-dimensional ͑6D͒ potential energy surface was taken from density functional theory calculations using the generalized gradient approximation and a slab representation of the metal surface. The 6D calculations show that out-of-plane diffraction is very efficient, at the cost of in-plane diffraction, as was the case in previous four-dimensional ͑4D͒ calculations. This could explain why so little in-plane diffraction was found in scattering experiments, suggesting the surface to be flat, whereas experiments on reaction suggested a corrugated surface. Results of calculations for off-normal incidence of (vϭ0,jϭ0) H 2 show that initial parallel momentum inhibits dissociation at low normal translational energies, in agreement with experiment, but has little effect for higher energies. Reaction of initial (vϭ1,jϭ0) H 2 is predicted to be vibrationally enhanced with respect to (v ϭ0,jϭ0) H 2 , as was also found in three-dimensional ͑3D͒ and 4D calculations, even though H 2 ϩPt(111) is an early barrier system.

“…In an attempt to account for lost flux, they did, however, remark that reaction could play a significant role in the attenuation of their signal. Since the reaction probability at the energy considered has been shown to be relatively small in both theoretical calculations 33 and experiments on H 2 and D 2 on Pt͑111͒, 12,13 it is more likely that the greater part of the loss of flux in Cowin's experiment should be attributed to other causes, such as out-of-plane diffraction ͑see Sec. III C͒.…”

Section: A Reactionmentioning

confidence: 99%

“…Since the early 1980s, the reactive, the rotationally elastic and inelastic, and the diffractive scattering of molecular hydrogen from metal surfaces have been studied extensively, both experimentally [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and theoretically. [17][18][19][20][21][22][23][24][25][26][27][28] Much attention has been devoted to HD scattering from Pt͑111͒ because of, inter alia, the high probabilities for rotational excitation to only a limited number of accessible rotational states.…”

Section: Introductionmentioning

confidence: 99%

Diffractive and reactive scattering of (v=0, j=0) HD from Pt(111): Six-dimensional quantum dynamics compared with experiment

Kingma

Somers

Pijper

et al. 2003

We present results of (vϭ0, jϭ0) HD reacting on and scattering from Pt͑111͒ at off-normal angles of incidence, treating all six molecular degrees of freedom quantum mechanically. The six-dimensional potential energy surface ͑PES͒ used was obtained from density functional theory, using the generalized gradient approximation and a slab representation of the metal surface. Diffraction and rotational excitation probabilities are compared with experiment for two incidence directions, at normal incidence energies between 0.05-0.16 eV and at a parallel translational energy of 55.5 meV. The computed ratio of specular reflection to nonspecular in-plane diffraction for HDϩPt͑111͒ is lower than found experimentally, and lower for HDϩPt͑111͒ than for H 2 ϩPt(111) for both incidence directions studied. The calculations also show that out-of-plane diffraction is much more efficient than in-plane diffraction, underlining that results from experiments that solely attempt to measure in-plane diffraction are not sufficient to show the absence of surface corrugation. Discrepancies in rotational excitation and diffraction probabilities between theory and experiment are discussed, as well as possible future improvements in the dynamical model and in the calculation of the PES.