Theoretical Studies of the Dynamics of Gases at Organic Surfaces

Apr
04
2014
10:00 AM - 11:00 AM
Diego Troya, Virginia Tech, Blacksburg, Virginia
Chemical Sciences Division Seminar
Chemical and Materials Sciences Building (4100), Room C-201
CONTACT :
Email: Deen Jiang
Phone:865.574.5199
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Collisions between gases and organic surfaces are ubiquitous. However, our fundamental atomistic understanding of the factors that control the dynamics in collisions of simple gas-phase molecules with condensed-phase organics is still shallow. In recent time, a variety of experimental approaches have revealed intimate aspects of gas/organic surface collisions, including the amount of energy transferred between the gas and the surface, the reaction probabilities, and the energy and angular distributions of the desorbing products after collision. These experimental studies have made use of molecular beams directed at surfaces placed in ultrahigh vacuum chambers and time-of-flight or spectroscopic detection of gas products. In this talk, theoretical work that has been developed in recent time to capture these experiments will be reviewed. The simulations involve classical trajectory calculations of gas/surface collisions in which the potential-energy surfaces required for the trajectory propagation are derived from high-accuracy ab initio calculations. For inelastic collisions, standard harmonic forcefields with improved non-bonding terms reproduce experiments on rare gas, O2, and N2 collisions with alkanethiol self-assembled monolayers (SAMs) with high fidelity. For reactive collisions, a direct-dynamics QM/MM approach that involves parametric electronic structure methods has been utilized to simulate the reactions of fluorine radicals with SAMs. This latter approach makes it possible to investigate the dynamics of reactive gas/organic surface collisions with unprecedented levels of accuracy.

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