Rotational effects on the dissociation dynamics of CHD₃ on Pt(111)

Abstract

Dissociation of methane on metal surfaces is of high practical and fundamental interest. Therefore there is currently a big push aimed at determining the simplest dynamical model that allows the reaction dynamics to be described with quantitative accuracy using quantum dynamics. Using five-dimensional quantum dynamical and full-dimensional ab initio molecular dynamics calculations, we show that the CD3 umbrella axis of CHD3 must reorient before the molecule reaches the barrier for C-H cleavage to occur in reaction on Pt(111). This rules out the application of the rotationally sudden approximation, as explicitly shown through a comparison with calculations using this approximation. Further, we suggest that the observed umbrella swing should strongly affect the sensitivity of C-H cleavage to the initial alignment of the molecule relative to the surface as found experimentally for closely related systems. We find very large differences in reactivity for molecules pre-excited to different rotational states, particularly if these states are associated with different orientations of the C-H bond.

Transferability of the SRP32-vdW specific reaction parameter functional to CHD3 dissociation on Pt(110)-(2 × 1)

“…The initial distributions for θ and β both resemble sine distributions showing that the initial conditions are correctly sampled. As for methane dissociation on Pt(111) 52,79 and Pt(211), 52 Fig. 11(a) shows that the dissociating bond has to be oriented towards the surface for dissociation to occur, with the maximum reactivity seen around the value of θ for the L2 transition state.…”

Improved on-the-Fly MCTDH Simulations with Many-Body-Potential Tensor Decomposition and Projection Diabatization

“…[1][2][3][4][5][6] In MCTDH, the time-dependent Schrödinger equation (TDSE) is solved by introducing a wavefunction ansatz comprising a sum of Hartree products of single-particle functions (SPFs), along with their complex expansion coefficients; using the Dirac-Frenkel time-dependent variational principle, [7][8][9] one can then derive equations-of-motion for both the expansion coefficients and the SPFs, leading to an efficient method for propagating wavepackets which can, in principle, be converged to the exact quantum-mechanical result. The range of systems modelled to date with MCTDH is continually growing, spanning non-adiabatic dynamics in organic molecules, 2,10,11 transport on model surfaces, [12][13][14] and organometallic complexes. 15,16 In practice, two important general factors have constrained the application domain of MCTDH simulations.…”

Methane on a stepped surface: Dynamical insights on the dissociation of CHD3 on Pt(111) and Pt(211)

“…The dissociative chemisorption of methane on a transition metal surface has been employed, both theoretically [1][2][3][4][5][6][7][8][9][10] and experimentally [11][12][13][14] , as a model system to understand one of the most important steps in steam reforming 15 , a fundamental industrial process which is currently one of the most common ways to produce molecular hydrogen. The CH bond cleavage on a Ni or Pt based catalyst is believed to be one of the rate determining steps 15 of the overall process in the high temperature regime.…”