Search Results

Systematic Approaches to Predictive Computational Chemistry using the Correlation Consistent Basis Sets

Description: The development of the correlation consistent basis sets, cc-pVnZ (where n = D, T, Q, etc.) have allowed for the systematic elucidation of the intrinsic accuracy of ab initio quantum chemical methods. In density functional theory (DFT), where the cc-pVnZ basis sets are not necessarily optimal in their current form, the elucidation of the intrinsic accuracy of DFT methods cannot always be accomplished. This dissertation outlines investigations into the basis set requirements for DFT and how the intrinsic accuracy of DFT methods may be determined with a prescription involving recontraction of the cc-pVnZ basis sets for specific density functionals. Next, the development and benchmarks of a set of cc-pVnZ basis sets designed for the s-block atoms lithium, beryllium, sodium, and magnesium are presented. Computed atomic and molecular properties agree well with reliable experimental data, demonstrating the accuracy of these new s-block basis sets. In addition to the development of cc-pVnZ basis sets, the development of a new, efficient formulism of the correlation consistent Composite Approach (ccCA) using the resolution of the identity (RI) approximation is employed. The new formulism, denoted 'RI-ccCA,' has marked efficiency in terms of computational time and storage, compared with the ccCA formulism, without the introduction of significant error. Finally, this dissertation reports three separate investigations of the properties of FOOF-like, germanium arsenide, and silicon hydride/halide molecules using high accuracy ab initio methods and the cc-pVnZ basis sets.
Date: May 2009
Creator: Prascher, Brian P.
Partner: UNT Libraries

Performance of Density Functional Theory for 3d Transition Metal-Containing Complexes: Utilization of the Correlation Consistent Basis Sets

Description: Article discussing the performance of density functional theory for 3d transition metal-containing complexes and the utilization of the correlation consistent basis sets.
Date: July 2, 2009
Creator: Tekarli, Sammer M.; Drummond, Michael L.; Williams, T. Gavin; Cundari, Thomas R., 1964- & Wilson, Angela K.
Partner: UNT College of Arts and Sciences

Activation of Carbon-Hydrogen and Hydrogen-Hydrogen Bonds by Copper-Nitrenes: A Comparison of Density Functionality Theory with Single- and Multireference Correlation Consistent Composite Approaches

Description: Article on a comparison of density functional theory with single- and multireference correlation consistent composite approaches (ccCA).
Date: October 19, 2009
Creator: Tekarli, Sammer M.; Williams, T. Gavin & Cundari, Thomas R., 1964-
Partner: UNT College of Arts and Sciences

Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)2M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}2N] and [(TMS)2NFe]2(smif)2

Description: Article discussing unusual electronic features and reactivity of the dipyridylazaallyl ligand and characterizations of (smif)2M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}2N and [(TMS)2NFe] 2(smif)2.
Date: February 19, 2009
Creator: Frazier, Brenda A.; Wolczanski, Peter T.; Lobkovsky, Emil B. & Cundari, Thomas R., 1964-
Partner: UNT College of Arts and Sciences

Chiral Steering of Molecular Organization in the Limit of Weak Adsorbate-Substrate Interactions: Enantiopure and Racemic Tartaric Acid Domains on Ag(111)

Description: Article on the chiral steering of molecular organization in the limit of weak adsorbate-substrate interactions.
Date: April 23, 2010
Creator: Santagata, Nancy M.; Lakhani, Amit M.; Davis, Bryce F.; Luo, Pengshun; Buongiorno Nardelli, Marco & Pearl, Thomas P.
Partner: UNT College of Arts and Sciences

Metals in Chemistry and Biology: Computational Chemistry Studies

Description: Numerous enzymatic reactions are controlled by the chemistry of metallic ions. This dissertation investigates the electronic properties of three transition metal (copper, chromium, and nickel) complexes and describes modeling studies performed on glutathione synthetase. (1) Copper nitrene complexes were computationally characterized, as these complexes have yet to be experimentally isolated. (2) Multireference calculations were carried out on a symmetric C2v chromium dimer derived from the crystal structure of the [(tBu3SiO)Cr(µ-OSitBu3)]2 complex. (3) The T-shaped geometry of a three-coordinate β-diketiminate nickel(I) complex with a CO ligand was compared and contrasted with isoelectronic and isosteric copper(II) complexes. (4) Glutathione synthetase (GS), an enzyme that belongs to the ATP-grasp superfamily, catalyzes the (Mg, ATP)-dependent biosynthesis of glutathione (GSH) from γ-glutamylcysteine and glycine. The free and reactant forms of human GS (wild-type and glycine mutants) were modeled computationally by employing molecular dynamics simulations, as these currently have not been structurally characterized.
Date: May 2007
Creator: Dinescu, Adriana
Partner: UNT Libraries

Thermodynamic Properties of Quinoxaline-1,4-Dioxide Derivatives: A Combined Experimental and Computational Study

Description: Article on thermodynamic properties of quinoxaline-1,4-dioxide derivatives and a combined experimental and computational study.
Date: March 16, 2004
Creator: Silva, Maria D. M. C. Ribeiro da; Gomes, José R. B.; Gonçalves, Jorge M.; Sousa, Emanuel A.; Pandey, Siddharth & Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

Carbon-Oxygen Bond Formation via Organometallic Baeyer-Villiger Transformations: A Computational Study on the Impact of Metal Identity

Description: Article discussing a computational study on the impact of metal identity and carbon-oxygen bond formation via organometallic Baeyer-Villiger transformations.
Date: December 20, 2011
Creator: Figg, Travis M.; Webb, Joanna R.; Cundari, Thomas R., 1964- & Gunnoe, T. Brent
Partner: UNT College of Arts and Sciences

Thermochemical and Theoretical Studies of Dimethylpyridine-2,6-dicarboxylate and Pyridine-2,3-, Pyridine-2,5-, and Pyridine-2,6-dicarboxylic Acids

Description: Article discussing thermochemical and theoretical studies of dimethylpyridine-2,6-dicarboxylate and pyridine-2,3-, pyridine-2,5- and pyridine-2,6-dicarboxylic acids.
Date: May 6, 2005
Creator: Matos, M. Agostinha R.; Morais, Victor M. F.; Silva, Maria D. M. C. Ribeiro da; Marques, Marta C. F.; Sousa, Emanuel A.; Castiñeiras, Jorge P. et al.
Partner: UNT College of Arts and Sciences

From Development of Semi-empirical Atomistic Potentials to Applications of Correlation Consistent Basis Sets

Description: The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. The computational accuracy with regard to experiment is reported.
Date: May 2014
Creator: Gibson, Joshua S.
Partner: UNT Libraries