CH4 dissociation on metals: a quantum dynamics model

CH4 dissociation on Ni(100): Comparison of a direct dynamical model to molecular beam experiments

“…1 and ⌬V* represents the increase in barrier from steric hindering due to less than optimal impact parameters or orientational angles. For lack of any more definitive information, we simply assume that ⌬V* is distributed according to a Gaussian, f (⌬V*)ϭe Ϫ(⌬V*Ϫ⌬ 0 ) 2 /W 2 . We choose ⌬ 0 ϭ0.4 eV and Wϭ0.2 eV to insure a gradual turn on of barriers generally consistent with the experimental widths observed in Paper I, as well as many other experimental systems.…”

“…The fact that such Arrhenius plots often do not measure true barrier heights has been stressed previously. 2,6 At isothermal conditions (T g ϭT s ) and at sufficiently high T ͑or wide barriers͒ so that tunneling is completely unimportant, then traditional transition state theory may provide an approximation to the isothermal rate of reaction for this mechanism of direct dissociation. Naturally transition state theory can say nothing about the molecular beam experiments under nonequilibrium initial conditions.…”

“…Luntz and Harris 2 have previously discussed in some detail a dynamical model for a mechanism of direct alkane dissociation on transition metal surfaces. This model is based on solving for the direct dissociation dynamics quantum mechanically on a reasonable reduced dimensionality PES for a quasidiatomic R-H interacting with a dynamic metal surface.…”

“…With a PES where the barrier was largely entrance channel dominated, reasonable qualitative agreement was obtained between the model and molecular beam experiments for the dissociation of CH 4 on Pt͑111͒, as well as with a variety of other molecular beam and thermal experiments. 2 In this paper, the reduced dimensionality dynamical model is developed for a PES with an exit channel barrier. In addition, steric factors ͑multidimensionality͒ are accounted for statically via the so-called ''hole'' approximation.…”

Energy dissipation and scattering angle distribution analysis of the classical trajectory calculations of methane scattering from a Ni(111) surface

“…Wave packet simulations of the methane dissociation reaction on transition metals have treated the methane molecule always as a diatomic up to now. [15][16][17][18][19][20] Apart from one C-H bond ͑a pseudo 3 stretch mode͒ and the molecule surface distance, either ͑mul-tiple͒ rotations or some lattice motion were included. None of these studies have looked at the role of the other internal vibrations, so there is no model that describes which vibrationally excited mode might be responsible for the experimental observed vibrational activation.…”