Eighth Condensed Phase and Interfacial Molecular Science (CPIMS)

eactive than the Ni, experiment suggests that the difference is even larger than our study found.
On both metals, the transition state is over the top site. However, on Ni, the methyl group moves
towards a hollow site during the reaction, while on Pt the methyl remains at the top site. This
behavior, if included in the model, should lead to a further lowering of the reactivity for Ni
relative to Pt, as the heavy methyl group does not tunnel as effectively as the H. This motion is
included in our full 15-dimensional RPH study of Ni(111), and we plan to do a similar study on
Pt(111). However, this has been put on hold by some recent (unpublished) experimental results
from the Beck group that suggest that the barrier to dissociation varies with product coverage on
the surface. This suggests that our DFT barrier heights may also vary with the size of our model
system. We are currently trying to sort this all out, as well as to elucidate the Beck experiments
Another study uses a purely classical RPH to examine methane reactions on Ni(100).
We are interested in how well classical mechanics works for this reaction, and will test various
perturbative and sudden approximations made in the quantum formulation. We are also
examining H-Ag scattering, subsurface penetration and thermal desorption, motivated by
experiments in the Wodtke group. A collaboration with the Kroes group will use AIMD to
examine CD3H reactions on Pt(111), in connection with on-going experiments in the Beck group.
We also continue to explore ways to extend our more “standard” quantum scattering approaches.
In particular, we are looking at ways to average over impact sites and better describe vibrational
motion. We are constructing a PES for CD3H chemisorption on Ni(111), treating the molecule as
a pseudo-diatomic by having the (unreactive) CD3 group evolve adiabatically, but correctly
including the zero point energy effects in the 6-dimensional Hamiltonian. Finally, we have
derived a fully quantum model for the time evolution of a scattering molecule coupled to the
electronic excitations of a metal substrate, using reduced density matrix methodologies. We have
yet to compute the electronically non-adiabatic couplings, and hope to initially examine the case
of H-metal scattering and sticking.
References
[1]. A. K. Tiwari, S. Nave and B. Jackson," Methane dissociation on Ni(111): A new
understanding of the lattice effect,” Phys. Rev. Lett. 103, 253201 (2009).
[2]. S. Nave, A. K. Tiwari and B. Jackson," Methane dissociation on Ni(111), Pt(111), Ni(100),
Pt(100) and Pt(110)-(1x2): Energetic study,” J. Chem. Phys. 132, 054705 (2010).
[3]. A. K. Tiwari, S. Nave and B. Jackson," The temperature dependence of methane dissociation
on Ni(111) and Pt(111): Mixed quantum-classical studies of the lattice response,” J. Chem. Phys.
132, 134702 (2010).
[4]. S. Nave and B. Jackson," Vibrational mode-selective chemistry: Methane dissociation on
Ni(100)” Phys. Rev. B 81, 233408 (2010).
[5]. B. Lepetit, D. Lemoine, Z. Medina, and B. Jackson, “Sticking and desorption of hydrogen on
graphite: a comparative study of different models,” J. Chem. Phys. 134, 114705 (2011).
[6] B. Jackson and S. Nave, "The dissociative chemisorption of methane on Ni(100): Reaction
path description of mode-selective chemistry” J. Chem. Phys. 135, 114701 (2011).
[7] B. Lepetit and B. Jackson, “Sticking of hydrogen on supported and suspended graphene at
low temperature,” Phys. Rev. Lett. 107, 236102 (2011).
[8] Effect of surface motion on the rotational quadrupole alignment parameter of D 2 reacting on
Cu(111), F. Nattino, C. Díaz, B. Jackson, and G.J. Kroes, Phys. Rev. Lett. 108, 236104 (2012).
[9] B. Jackson, “The effects of lattice motion on gas-surface reactions”, in Dynamics of Gas-
Surface Interactions: Atomic-level understanding of scattering processes at surfaces, Springer
Series in Surface Sciences, R. D. Muiño and H. F. Busnengo, eds., (accepted).
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