Rotational motion and the dissociation of H2 on Cu(111)

A two-dimensional ͑2-D͒ potential energy surface ͑PES͒ has been calculated for H 2 interacting with the ͑100͒ face of copper. The PES is for H 2 approaching with its internuclear axis parallel to the surface and dissociating over a bridge site into neighboring hollow sites. The density functional calculations were performed both within the local density approximation ͑LDA͒ and within a generalized gradient approximation ͑GGA͒. The LDA surface shows no barrier to chemisorption, but the GGA surface has a barrier of height 0.4 eV. A fit of the GGA surface has been used to calculate reaction probabilities for H 2 in its vϭ0 and vϭ1 vibrational states, employing a wave packet method. The 2-D wave packet results for the vϭ0 and vϭ1 thresholds are consistent with experiment, indicating that the barrier height calculated within the GGA used is accurate. The GGA results for the value of the barrier height are also consistent with the GGA value ͑0.

Section: B Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dissociation of H2 on Cu(100): Dynamics on a new two-dimensional potential energy surface

Wiesenekker

Kroes

Baerends

et al. 1995

“…For many H 2 ϩmetal surface systems, the reaction probability depends on the initial angular momentum of the incident molecule, which will broaden the reaction probability curve in an molecular beam experiment relative to the computational results for jϭ0. 41,43,50,63-65 Presently, we have results for too few FIG. 8.…”

Section: E Comparison With Experiment: Reactionmentioning

confidence: 99%

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.

“…[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. Experimental efforts by Cowin and co-workers 1,2 have been followed by several theoretical studies of this system, employing either Wigner R-matrix theory 27,29 or EngdahlMoiseyev-Maniv T-matrix methods 28 to obtain rotationally inelastic scattering probabilities.…”

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.