Reactive scattering of H2 on Cu(111) at 925 K: Effective hartree potential vs sudden approximation

** Authors:

B. Smits
M. K. Sah
K. Naskar
S. Adhikari
J. Meyer
M. F. Somers

** Contact e-mail:

b.smits@lic.leidenuniv.nl
j.meyer@chem.leidenuniv.nl
m.somers@chem.leidenuniv.nl

** Abstract:

We present new quantum dynamical results for the reactive scattering of hydrogen molecules from a Cu(111) surface at a surface temperature of 925 K.
Reaction, scattering, and diffraction probabilities are compared for results obtained from both an effective Hartree potential (EfHP) and a sudden approximation approach, implemented through the static corrugation model (SCM), to include surface temperature effects.
Towards this goal, we show how the SRP48 DFT-functional and an emebbed atom potential perform when used to caclulate copper lattice constants and thermal expansion coefficients based on lattice dynamics calculations within the quasi-harmonic approximation.
The so-calculated phonons are then used in the EfHP approach to replace the normal modes of a fictitious copper cluster used in earlier work.
We find that both the EfHP and SCM approaches correctly predict the reaction probability curve broadening effect when the surface temperature is increased.
Similarly, results from rovibrationally elastic scattering appear to be improved, predominantly from the SCM model.
The behavior of the EfHP results appears to remain much closer to that of a Born-Oppenheimer static surface approach, which excludes any surface temperature effects.
Finally, for the diffraction, we show very clear attenuation effects for the SCM approach, significantly decreasing specular diffraction probabilities at 925 K surface temperature.
These results demonstrate that state-of-the-art theoretical models are able to reproduce strictly quantum mechanical scattering effects with a sudden approximation model and open up interesting oppertunities for further comparisons to experimental diffraction results.


** Folder FIG1_TAB1:
Datafiles used in the figure. QD results are thermal expansion, experimental data is linear thermal expansion.
MD results only contain lattice constants. Lattice constants for (b) are derived from the thermal expansion values, as is the extrapolation, for the initial 0K value.
Values in the Table are also derived from the thermal expansion and 0K lattice constant.

** Folder FIG2:

Datafiles used in the figure. Results obtained from phonopy output.
Units for frequency (first column) are THz.

** Folder FIG34:

Data used in the figure excluding experimental results (see experimental reference for fitted form and its parameters).
Included are the normal incidence energy (in eV), reaction probabilities, and rovib scattering to all states that gave a non-zero probability.

** Folder FIG5:

Data used in the figure.
Included are the incidence energy (in eV), reaction probablities, and the diffraction probabilities to every state with a non-zero probability.
Diffraction was summed over all final rovib states.