Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111)
Open Access
- Author:
- Mubin, Shafat A
- Graduate Program:
- Physics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 24, 2016
- Committee Members:
- Kristen Ann Fichthorn, Dissertation Advisor/Co-Advisor
Kristen Ann Fichthorn, Committee Chair/Co-Chair
Milton Walter Cole, Committee Member
Jorge Osvaldo Sofo, Committee Member
Adrianus C Van Duin, Outside Member - Keywords:
- Benzene
Monolayer
Desorption
Accelerated MD
Bond-boost Method
Force-field
Order-disorder
Ag(111)
TPD
Substrate-mediated Interaction
Molecular Dynamics
Surface Defects - Abstract:
- The adsorbed layer of benzene on Ag(111) is studied using molecular dynamics techniques. A force-field is developed to describe benzene-Ag interaction, involving the introduction of a fictitious site at the center of benzene, and the binding energy $E_b$=0.64 eV and the vanishing coverage prefactor of desorption $k_0$ = $(5.0\pm3.0)\times10^{14} \ s^{-1}$ are obtained from the force-field. Subsequently, the intermolecular interaction is studied and found to be dominated by substrate-mediated interactions, primarily the pairwise interaction between adsorbates produced by scattering of Shockley states. The z-dependence of these substrate-mediated interactions is derived and found to create noticeable difference to the order-disorder transition temperature of the adsorbed benzene monolayer. These substrate-mediated interactions are further validated by simulating high-coverage temperature-programmed desorption (TPD) spectra. In simulating high-coverage TPD, the bond-boost method is used to boost the simulated timescale several orders of magnitude. In the process, the impact of surface defects on TPD spectra is also investigated, and found to slightly shift the peak desorption temperatures and considerably broaden the trailing edge of the spectra.