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Effect of the Ar–Ni(s) potential on the cross section for Ar + CH 4 / Ni {111} collision- induced desorption and the need for a more accurate CH 4 / Ni {111} potential
Journal of Chemical Physics (2005)
  • Lipeng Sun, Northwestern University
  • Kirk A. Peterson, Washington State University
  • Yuri Alexeev, Pacific Northwest National Laboratory
  • Theresa L. Windus, Pacific Northwest National Laboratory
  • James Kindt, Emory University
  • William L. Hase, Texas Tech University
Abstract
In a previous paper [L. Sun, P. de Sainte Claire, O. Meroueh, and W. L Hase, J. Chem. Phys. 114, 535 (2001)], a classical trajectory simulation was reported of CH4desorption from Ni{111} by Ar-atom collisions. At an incident angle θi of 60° (with respect to the surface normal), the calculated collision-induced desorption (CID) cross sections are in excellent agreement with experiment. However, for smaller incident angles the calculated cross sections are larger than the experimental values and for normal collisions, θi=0°, the calculated cross sections are approximately a factor of 2 larger. This trajectory study used an analytic function for the Ar+Ni(s)intermolecular potential which gives an Ar–Ni{111} potential energy minimum which is an order of magnitude too deep. In the work reported here, the previous trajectory study is repeated with an Ar+Ni(s) analytic intermolecular potential which gives an accurate Ar–Ni{111} potential energy minimum and also has a different surface corrugation than the previous potential. Though there are significant differences between the two Ar+Ni(s) analytic potentials, they have no important effects on the CID dynamics and the cross sections reported here are nearly identical to the previous values. Zero-point energy motions of the surface and the CH4–Ni(s) intermolecular modes are considered in the simulation and they are found to have a negligible effect on the CID cross sections. Calculations of the intermolecular potential between CH4 and a Ni atom, at various levels of theory, suggest that there are substantial approximations in the ab initio calculation used to develop the CH4+Ni{111} potential. The implication is that the differences between the trajectory and experimental CID cross sections may arise from an inaccurate CH4+Ni{111} potential used in the trajectory simulation.
Keywords
  • nickel,
  • intermolecular potential energy surfaces,
  • desoption,
  • intermolecular potentials,
  • potential energy surfaces
Publication Date
2005
DOI
10.1063/1.1829993
Publisher Statement
The following article appeared in Journal of Chemical Physics 122, 4 (2005); and may be found at, doi: 10.1063/1.1829993.

Copyright 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Citation Information
Lipeng Sun, Kirk A. Peterson, Yuri Alexeev, Theresa L. Windus, et al.. "Effect of the Ar–Ni(s) potential on the cross section for Ar + CH 4 / Ni {111} collision- induced desorption and the need for a more accurate CH 4 / Ni {111} potential" Journal of Chemical Physics Vol. 122 Iss. 4 (2005) p. 44704 - 44710
Available at: http://works.bepress.com/theresa-windus/12/