Reactive scattering of H2 from Cu(100): Comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment

Abstract

We present new experimental and theoretical results for reactive scattering of dihydrogen from Cu(100). In the new experiments, the associative desorption of H 2 is studied in a velocity resolved and final rovibrational state selected manner, using time-of-flight techniques in combination with resonance-enhanced multi-photon ionization laser detection. Average desorption energies and rotational quadrupole alignment parameters were obtained in this way for a number of (v = 0, 1) rotational states, v being the vibrational quantum number. Results of quantum dynamics calculations based on a potential energy surface computed with a specific reaction parameter (SRP) density functional, which was derived earlier for dihydrogen interacting with Cu (111), are compared with the results of the new experiments and with the results of previous molecular beam experiments on sticking of H 2 and on rovibrationally elastic and inelastic scattering of H 2 and D 2 from Cu(100). The calculations use the Born-Oppenheimer and static surface approximations. With the functional derived semi-empirically for dihydrogen + Cu(111), a chemically accurate description is obtained of the molecular beam experiments on sticking of H 2 on Cu(100), and a highly accurate description is obtained of rovibrationally elastic and inelastic scattering of D 2 from Cu(100) and of the orientational dependence of the reaction of (v = 1, j = 2 − 4) H 2 on Cu(100). This suggests that a SRP density functional derived for H 2 interacting with a specific low index face of a metal will yield accurate results for H 2 reactively scattering from another low index face of the same metal, and that it may also yield accurate results for H 2 interacting with a defected (e.g., stepped) surface of that same metal, in a system of catalytic interest. However, the description that was obtained of the average desorption energies, of rovibrationally elastic and inelastic scattering of H 2 from Cu(100), and of the orientational dependence of reaction of (v = 0, j = 3 − 5, 8) H 2 on Cu(100) compares less well with the available experiments. More research is needed to establish whether more accurate SRP-density functional theory dynamics results can be obtained for these observables if surface atom motion is added to the dynamical model. The experimentally and theoretically found dependence of the rotational quadrupole alignment parameter on the rotational quantum number provides evidence for rotational enhancement of reaction at low translational energies.

The effect of the exchange-correlation functional on H2 dissociation on Ru(0001)

“…Examples of such experiments include associative desorption experiments, which by application of detailed balance may yield initial state-resolved reaction probabilities (measured for, for instance, H 2 60 and D 2 93, 98 dissociation on Cu(111)). Alternatively, such experiments may also yield rotational state populations (as measured for H 2 + Pd(100) 99 ), average translational energies for H 2 desorbing from the surface in particular (v, J) states (as measured for H 2 + Cu(100) 20 ) and initial rotational quadrupole alignment parameters describing the orientational dependence of reaction (measured for, for instance, H 2 + Cu(111), 100-102 H 2 + Cu(100), 20 and H 2 + Pd(100) 103 ). Additional valuable information can perhaps be obtained from experiments that use laser excitation and detection using resonance enhanced multi-photon ionization (REMPI) to determine probabilities for rotationally inelastic scattering, like the experiments performed earlier for H 2 + Cu(111), 104 H 2 , 105 HD, 106 and D 2 107 + Cu(100) and H 2 , 108 HD, 106 and D 2 107 + Pd(111).…”

“…The functional that was obtained as a result of the SRP procedure for H 2 on Cu(111) was also found to work well for H 2 on Cu(100). 20 In the SRP procedure previously used for H 2 on Cu(111), a parameter (α) mixing two functionals by 084702-2 M. Wijzenbroek and G. J. Kroes J. Chem.…”

Methane dissociation on Pt(111): Searching for a specific reaction parameter density functional

“…Our ultimate goal is to develop a semi-empirical density functional for this system, following the specific reaction parameter (SRP) approach. This approach, inspired by the work of Truhlar and coworkers [54,55], has been successfully applied to the reactive scattering of H 2 from low-index copper surfaces [4][5][6]. To be considered as such, a SRP functional for the system we consider here must in principle produce good agreement with the laser-off experimental reaction probabilities over the energy range for which data are available, and it must correctly predict the reactivity of the ν 1 = 1 vibrational state.…”

“…Many implementations of the GGA exist, differing in the approximate expression of the exchange-correlation functional (E XC ). Even though functionals at the GGA level are not expected to be accurate in predicting, for instance, the reaction barrier height for a given system (for gas phase reactions the lowest mean absolute error is 3.8 kcal/mol, as obtained with the MOHLYP2 functional [2,3]), semi-empirical versions of E XC allow one to produce accurate PESs through the fitting of one parameter to a single set of experimental data for H 2 -metal surface interactions [4][5][6][7].…”

Vibrationally Promoted Dissociation of Water on Ni(111)

“…The calculated sticking probabilities are thus a Boltzmann average of the contributions from these states. This approach has been used previously by Kroes and co-workers in their studies for H 2 dissociative chemisorption processes (42). For the simulation of state-resolved experiments, only the specific vibrational state (n 3 or 2n 3 ) prepared by the IR laser is considered.…”