

@mastersthesis {7169,
	title = {Molecular properties from ab initio quantum mechanics},
	year = {1995},
	note = {9606929},
	school = {Columbia University},
	type = {phdPh.{D}.},
	address = {Ann Arbor},
	abstract = {We first present an extensive study of including solvent effects in electronic structure calculations by using a continuum solvent model in a self-consistent reaction field (SCRF) methodology. Electronic correlation is included at the Generalized Valance Bond (GVB) level for a small set of solute molecules. The calculated solvation energies of some cases cannot be made to agree with experiment. A subsequent study using a much larger set of molecules investigates these discrepancies and new ones by computing the hydrogen bonding energies of a water molecule docked to solutes. These calculations reveal a major limitation of current continuum solvent theories and molecular mechanics force fields: hydrogen bonding energies in some cases are poorly modeled by electro-static interactions. An additive correction term is developed to be included in the solvation energies of these cases. Agreement with experimental solvation energies is greatly improved. A subsequent study presents SCRF results for the same set of solute molecules but uses a method based on the local MP2 (LMP2) wavefunction. Also, using gas-phase charges with this LMP2-based theory with the Generalized Born/Surface Area method requires a minimal adjustment of parameters to produce solvation energies in reasonable agreement with experiment. Nonlinear optical properties are also investigated. First, methods are presented for computing \${\textbackslash}alpha\$ and \${\textbackslash}beta\$ at the Hartree-Fock (HF) level. Timings compared to Gaussian 92 indicate significantly better scaling with system size. Preliminary results are also presented for including electronic correlation at the LMP2 level and solvation effects via a SCRF methodology. Subsequent studies present applications of chemical interest. The first is a study of a series of push-pull charge transfer molecules which have been shown experimentally to have the largest measured value of \${\textbackslash}beta\$ of any organic molecule. While calculations of these properties are not in quantitative agreement with experiment, they are in qualitative agreement with experiment. Next is a study of the saturation of the second nonlinear polarizability \${\textbackslash}gamma\$ for polyenes. Some of the largest molecules to date are studied at the ab initio level. Agreement with experiment is not reached in some cases. Finally, \${\textbackslash}beta\$ is computed for a series of helicenes in an attempt to screen them for large nonlinear optical effects before synthesis.},
	keywords = {0494:Chemistry, Chemistry, electronic structure, generalized valence bond, Pure sciences},
	url = {http://search.proquest.com/docview/304186977?accountid=14270},
	author = {Marten, Bryan David}
}
