Dynamics of CO2 Scattering off a Perfluorinated Self-Assembled Monolayer. Influence of the Incident Collision Energy, Mass Effects, and Use of Different Surface Models

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• 作者：Juan J. Nogueira ; Saulo A. Vzquez ; Oleg A. Mazyar ; William L. Hase ; Bradford G. Perkins ; ; David J. Nesbitt ; Emilio Martnez-Nez
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：April 23, 2009
• 年：2009
• 卷：113
• 期：16
• 页码：3850-3865
• 全文大小：710K
• 年卷期：v.113,no.16(April 23, 2009)
• ISSN：1520-5215

文摘

The dynamics of collisions of CO₂ with a perfluorinated alkanethiol self-assembled monolayer (F-SAM) on gold were investigated by classical trajectory calculations using explicit atom (EA) and united atom (UA) models to represent the F-SAM surface. The CO₂ molecule was directed perpendicularly to the surface at initial collision energies of 1.6, 4.7, 7.7, and 10.6 kcal/mol. Rotational distributions of the scattered CO₂ molecules are in agreement with experimental distributions determined for collisions of CO₂ with liquid surfaces of perfluoropolyether. The agreement is especially good for the EA model. The role of the mass in the efficiency of the energy transfer was investigated in separate simulations in which the mass of the F atoms was replaced by either that of hydrogen or chlorine, while keeping the potential energy function unchanged. The calculations predict the observed trend that less energy is transferred to the surface as the mass of the alkyl chains increases. Significant discrepancies were found between results obtained with the EA and UA models. The UA surface leads to an enhancement of the energy transfer efficiency in comparison with the EA surface. The reason for this is in the softer structure of the UA surface, which facilitates transfer from translation to interchain vibrational modes.