Computational studies of molecules adsorbed on surfaces

This dissertation contains the results of two different computational studies of adsorbed species. The dissertation is composed of two parts. In the first part we present research aimed at understanding the structural and dynamical properties of a single, partially adsorbed, model polymer chain. In the second part, we present research aimed at determining the minimum energy configuration of a single methane molecule adsorbed on the (100) face of MgO.; In the polymer study we simulated the dynamics of a single polymer chain partially adsorbed on an impenetrable surface using two dynamic Monte Carlo algorithms: the Local Jump (LJ) algorithm and the Bond Fluctuation (BF) algorithm. The objectives of this research were three-fold: (1) to determine the structural and dynamical scaling exponents for a partially adsorbed polymer chain; (2) to determine if the Rouse normal coordinates are the appropriate normal coordinates for a partially adsorbed chain; (3) to determine if the LJ and BF algorithms provide similar descriptions of the dynamics of a partially adsorbed polymer chain.; The results of our polymer research show that the internal dynamics of a chain simulated using the LJ algorithm is different than that of a chain simulated using the BF algorithm. Using both algorithms we determined that the Rouse normal coordinates are not the appropriate normal coordinates for a partially adsorbed polymer chain.; In the methane-MgO study high level ab initio calculations were performed to investigate the electrostatic energy of a single methane molecule adsorbed on MgO(100). Two adsorption geometries were considered: edge-down (C2v axis perpendicular to the MgO(100) surface) and face-down (C3v axis perpendicular to the surface). These ab initio calculations indicate the edge-down configuration is significantly more favored than the face-down configuration, and that a single methane molecule in the near surface electric field of MgO experiences significant polarization effects. The focus of this work was to determine if three common empirical schemes could be used to reproduce the ab initio results. Each of the empirical models is shown to be in disagreement with the electrostatic energies calculated using ab initio methods.