Theoretical study of the dynamics of collisions between HCl and ω-hydroxylated alkanethiol self-assembled monolayers


We present a classical-trajectory study of collisions of HCl with hydroxylated alkanethiol self-assembled monolayers. The potential-energy surface used in the trajectory propagation is a combination of the standard OPLS force field to describe the surface and an analytical potential for the gas/surface interaction developed in this work. The gas/surface potential has been derived based on high-quality electronic-structure calculations of model HCl-alcohol systems in the gas phase and includes a flexible Buckingham term and a Coulombic term. The results of the trajectories calculations are in good agreement with recent molecular-beam experiments on the same system, thereby lending support to the accuracy of the calculations. The collision dynamics differ vastly from prior scattering studies involving rare gases and CO, primarily because the gas/surface attraction governed by hydrogen bonding dramatically increases the ability of the gas molecules to trap on the surface for extended times. The properties of the desorbing HCl molecules are largely insensitive to the initial collision energy and are only mildly affected by the incident angle. An analysis of the reaction mechanism reveals the distinct dynamics of trajectories that either recoil from the surface directly or undergo multiple collisions with the surface and result in thermalization. © 2011 American Chemical Society.

Publication Title

Journal of Physical Chemistry C