Ab initio characterization of chemical vapor deposition species
Larkin, Joseph Dennis
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In Chapter 2, density functional theory (DFT) and coupled cluster with peturbative triples (CCSD(T)) methods were used to determine the ground state equilibrium geometry of the aluminum-trimethylaluminum (AlTMA) complex. A monobridged molecular structure was originally proposed from experimental data (Chem. Phys. Lett. 2002, 360, 313) and characterized by our work; however this structure is not the lowest energy minima on the potential energy surface. An unanticipated H3C-Al-Al(CH3)2 geometry was found to be 2 kcal/mol lower in energy than the complex proposed through kinetics experiments. Chapters 3 and 4 present two studies aimed at describing the role that alkyl-, silyl-, and halo-substituents play in stablilizing electron affinities of silylenes and silyl radicals. The recent isolation of stable dialkylsilylenes (J. Am. Chem. Soc. 2003, 125, 3212) motivated the use of DFT and CCSD(T) methods with both DZP++ and the Dunning-Woon aug-cc-pVXZ series of basis sets to study these silicon systems. The addition of silyl- and bromo-substituents considerably increases the ability of both silylenes and silyl radicals to bind excess electrons. Chapter 5 details a structural investigation of the monomeric and dimeric forms of boronic acids. An endo-exo version of the monomer and a symmetric doubly hydrogen bonded isomer of the dimer were found to be the lowest energy structures at the DFT and MP2 level. Two monomeric isomers were found only 1.1 and 2.4 kcal/mol higher in energy than the endo-exo structure and for the dimers, a total of thirteen structures were found to be minima on the potential energy surface. Despite the large number of dimeric minima, only four were found to be within ~5 kcal/mol of the symmetric doubly H-bonded form.