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Probing the Hydrogen Bonding Interaction at the Gas-Surface Interface using Dispersion Corrected Density Functional Theory
Edwards, Angela Celeste
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he interactions of the chemical warfare agent sulfur mustard with amorphous silica were investigated using electronic structure calculations. In this thesis, the binding energies of sulfur mustard and mimic species used in the laboratory were calculated using density functional theory and fully ab initio calculations. The wB97XD and B97D functionals, which include functions to account for long-range dispersion interactions, were compared to experimental trends. The hydroxylated amorphous silica surface was approximated using a gas-phase silanol molecule and clusters containing a single hydroxyl moiety. Recent temperature programmed desorption experiments performed in UHV concluded that sulfur mustard and its less toxic mimics undergo molecular adsorption to amorphous silica. Hydrogen bonding can occur between surface silanol groups and either the sulfur or chlorine atom of the adsorbates, and the calculations indicate that the binding energies for the two hydrogen bond acceptors are similar. The adsorption of sulfur mustard and its mimics on silica also exhibits the presence of significant van der Waals interactions between alkyl of the adsorbates and the surface. These interactions, in combination with the formation of a hydrogen bond between a surface silanol group and the Cl or S atoms of the adsorbates, provide remarkably large binding energies.
- Masters Theses