The dissociation of methane on transition metals is an important reaction in catalysis. It is the rate limiting step in steam reforming to produce syngas. Molecular beam experiments have shown that the energy in the internal vibrations are about as effective as the translational energy in inducing dissociation.
The published wave packet simulations on the methane dissociation reaction on transition metals have treated the methane molecule always as a diatomic up to now. Besides the C-H bond and molecule surface distance, a combination of other coordinates were included, like (multiple) rotations and some lattice motion. None of them have looked at the role of the internal vibrations. We were not able yet to simulate the dissociation including all internal vibrations. Instead we simulated the scattering of methane in fixed orientations, for which all internal vibrations can be included, and used the results to deduce consequences for the dissociation. Furthermore we studied the isotope effect, and the role of vibrational excitations.
We ended with classical trajectory calculations of the rotational vibrational scattering of a non-rigid methane molecule from a Ni(111) surface. Energy dissipation and scattering angles have been studied as a function of the translational kinetic energy, the incident angle, the (rotational) nozzle temperature, and the surface temperature.
Electrodynamical Forbiddance of Strong Quadrupole Light-Molecule Interaction in the Methane Molecule and its Manifestation in Surface Enhanced Hyper Raman Scattering Spectra
The microscopic mechanisms involved in the formation/dissociation of methane hydrate confined at the nanometer scale are unraveled using advanced molecular modeling techniques combined with a mesoscale thermodynamic approach. By means of atom-scale simulations probing coexistence upon confinement and free energy calculations, phase stability of confined methane hydrate is shown to be restricted to a narrower temperature and pressure domain than its bulk counterpart. The melting point depression at a given pressure, which is consistent with available experimental data, is shown to be quantitati…
We describe a fast implementation of the quasi-centroid molecular dynamics (QCMD) method in which the quasi-centroid potential of mean force is approximated as a separable correction to the classical interaction potential. This correction is obtained by first calculating quasi-centroid radial and angular distribution functions in a short path integral molecular dynamics simulation, and then using iterative Boltzmann inversion to obtain an effective classical potential that reproduces these distribution functions in a classical NVT simulation. We illustrate this approach with example applicatio…
Hydrophobic solutes significantly alters water hydrogen bond network. The local alteration of solvation struc-tures get reflected in the vibrational spectroscopic signal. Although it is possible to detect this microscopicfeatures by modern infrared spectroscopy, however, bulk phase spectra often comes with formidable challengeof establishing the connection among the experimental spectra to molecular structures. Theoretical spec-troscopy can serve as more powerful tool even where spectroscopic data cannot provide microscopic picture.In the present work, we build a theoretical spectroscopic map …
The fractional calculus framework will be used to invert the potential energy function from the classical scattering angle, which will be related to Riemann-Liouville fractional integral. Numerical solution of this fractional order problem will be applied to the inverse Rutherford scattering and to the inverse scattering of Xe--Rn atoms, in which the potential is given by Lennard-Jones function. Proofs of existence will be presented for more clarity and completness of the present work. In the two cases considered, the potential energy function can be retrieved with a desired precision. The pre…
