Density functional theory (DFT) calculations (using Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional (BLYP) and Becke's three-parameter hybrid DFT/HF method using Lee-Yang-Parr's correlation functional (B3LYP)) have been carried out to investigate the structure, dipole moment, and vibrational spectrum of azulene. Structural parameters obtained by both BLYP/6-31G* and B3LYP/6-31G* geometry optimization are in good agreement with available experimental data and show clearly the aromatic nature (bond equalization), a property the Hartree-Fock theory fails to describe correctly. The BLYP/6-31G* and B3LYP/6-31G* dipole moments are within experimental uncertainty and are in good agreement with results obtained from the much more expensive MP2 and MR-SDCI calculations. Most of the BLYP/6-31G* vibrational frequencies are in excellent agreement with available experimental assignments. On the basis of the calculated results, assignments of some missing frequencies in the experimental studies are proposed.

Ab initio Hartree-Fock and density functional theory calculations were carried out to investigate the structure and vibrational spectrum of 1,3-dithiole-2-thione. All the calculations predicted a planar structure with C2v symmetry. Harmonic force field and vibrational mode calculations provided convincing theoretical evidence for reassignments of some fundamental vibrational modes. The reassignments are in line with the observed polarization data of Dyer et al. This study shows that the density functional theory is a powerful tool for understanding the vibrational spectra of organic molecules.

Ab initio and density functional theory calculations confirm Craig's assignment of the fundamental vibrational modes of tetrafluorooxirane with the exception that assignments of the C-F stretching modes v9 (b1) and v13 (b2) should be exchanged. The calculated structural parameters are in good agreement with results of microwave studies except for the C-C bond length for which all the calculated results are slightly too long.

Density functional theory BLYP and ab initio HF calculations have been carried out to investigate the structures and vibrational spectra of dicyanobenzenes. The calculated results are in good agreement with reliable experimental data and indicate that the benzene rings of all three isomers are only slightly distorted by the two cyano groups. Vibrational frequencies calculated by BLYP/6-31G* force fields agree very well with experimental results, with a mean deviation of about 14 cm-1 for non-CH stretching modes. On the basis of agreement between the calculated and observed results, assignments of the fundamental vibrational modes were examined and some reassignments were proposed. This study demonstrates that the density functional theory BLYP calculation is a powerful approach to understanding the vibrational spectra of organic compounds.

The magnetic properties of axially confined, hydrogenated single-walled carbon nanotubes (SWCNTs) of the (n,0)-type with n=5-24 are systematically explored by density functional theory. Emphasis is placed on the relation between the ground-state magnetic moments of SWCNTs and zigzag graphene nanoribbons (ZGNRs). Comparison between the SWCNTs considered here and ZGNRs of equal length gives rise to two basic questions: 1) how does the nanotube curvature affect the antiferromagnetic order known to prevail for ZGNRs, and 2) to what extent do the magnetic moments localized at the SWCNT edges deviate from the zero-curvature limit of n/3 μB? In response to these questions, it is found that systems with n≥7 display preference for antiferromagnetic order at any length investigated, whereas for n=5, 6 the magnetic phase varies with tube length. Furthermore, elementary patterns are identified that describe the progression of the magnitude of the magnetic moment with n for the longest tubes explored in this work. The spin densities of the considered SWCNTs are analyzed as a function of the tube length L, with L ranging from 3 to 11 transpolyene rings for n≥7 and from 3 to 30 rings for n=5 and 6. Magnetic carbon nanostructures are explored by density functional theory calculations on axially confined, single-walled carbon nanotubes (SWCNTs) of the (n,0)-type with n=5-24. For SWCNTs with n≥7, antiferromagnetic (AFM) order is favored energetically over ferromagnetic (FM) order for all lengths L investigated, whereas for n=5, 6 the magnetic phase varies with tube length (see picture).

The magnetic properties of axially confined, hydrogenated single-walled carbon nanotubes (SWCNTs) of the (n,0)-type with n=5-24 are systematically explored by density functional theory. Emphasis is placed on the relation between the ground-state magnetic moments of SWCNTs and zigzag graphene nanoribbons (ZGNRs). Comparison between the SWCNTs considered here and ZGNRs of equal length gives rise to two basic questions: 1) how does the nanotube curvature affect the antiferromagnetic order known to prevail for ZGNRs, and 2) to what extent do the magnetic moments localized at the SWCNT edges deviate from the zero-curvature limit of n/3 μB? In response to these questions, it is found that systems with n≥7 display preference for antiferromagnetic order at any length investigated, whereas for n=5, 6 the magnetic phase varies with tube length. Furthermore, elementary patterns are identified that describe the progression of the magnitude of the magnetic moment with n for the longest tubes explored in this work. The spin densities of the considered SWCNTs are analyzed as a function of the tube length L, with L ranging from 3 to 11 transpolyene rings for n≥7 and from 3 to 30 rings for n=5 and 6. Magnetic carbon nanostructures are explored by density functional theory calculations on axially confined, single-walled carbon nanotubes (SWCNTs) of the (n,0)-type with n=5-24. For SWCNTs with n≥7, antiferromagnetic (AFM) order is favored energetically over ferromagnetic (FM) order for all lengths L investigated, whereas for n=5, 6 the magnetic phase varies with tube length (see picture).

Two classes of trimetal nitride metallofullerenes, Sc3N@C n (n=68, 78) and MxSc3-xN@C80 (x=0-2), are investigated by Density Functional Theory with respect to their electronic properties and related geometric, energetic, and magnetic features. The substantial electron transfer from the metallic core to the fullerene cage makes these systems promising candidates for nonlinear optical devices. Pronounced magnetic effects associated with complexes that enclose lanthanide constituents suggest their suitability as contrast agents in biomedical imaging.

The biodiesel industry produces millions of kilograms of low-value glycerol, which must be either stored or disposed of, creating environmental concerns. Even though glycerol is utilized as a raw material within various industries its supply is still superior to the demand. Upgrading this biodiesel by-product into value-added products using electrochemical technologies is a promising approach and will make biodiesel production more environmentally friendly with added financial benefits. Precious metals are the state-of-the-art electro-catalysts for the oxidation of organic compounds, and so are a logical choice for the electro-oxidation of glycerol. Two factors that hinder their use in this regard for commercial applications include their cost and susceptibility to poisoning by the carbonyl (CO) species formed during the electro-oxidation process. The use of inexpensive transition metals as the principal metals in a catalyst composite is thus appealing, leading to the selection of nickel (Ni). Furthermore, its high activity, anti-poison ability and long-term stability in alkaline solutions make it an attractive candidate for glycerol electrooxidation reaction (GEOR). The main thrust of this work is to develop a deeper understanding of the factors involved in controlling the selectivity of the product reaction without 3 carbon cleavage on non-precious metal surfaces. To overcome a trial-and-error approach, we took advantage of modern synthesis and characterization techniques for metal alloy nanoparticles and advances in rapid identifications and quantifications of products based on infrared spectroscopy. These tools were expected to provide the foundation for the detailed understanding of GEOR mechanism hence would pave the way for the rational design of catalysts to produce specific high value-added chemicals. We cared out extensive research to determine the effect of size, morphology, shape, support, experimental conditions and catalyst preparation methods on the catalytic performance of Ni. The thesis aims to demonstrate how the selectivity of unsupported Ni nanoparticles for GEOR can be improved via interaction of Ni with low noble and transition metals content. Enhanced selectivity towards C3 and C2 products such as glycerate, lactate, oxalate and tartronate, was achieved by simply adding less than 20 atomic percent of any of bismuth (Bi), Pd or Au onto Ni nanoparticles. Furthermore, the composition effect of carbon supported NiₓM₁₋ₓ (M = Bi, Pd and Au) nanomaterials were combined with Pt/C and commercial silver nanoparticles for cathodic hydrogen production and CO₂ electro-reduction, respectively. These rich-phase of Ni(OH)₂ catalysts were highly active and selective towards C-C bond breaking products leading to 100% selectivity of formate after 1 hr electrolysis and 100% conversion of glycerol after 24 hr at +1.55 V. Lastly, the first principles calculations based on the density functional theory (DFT) insights provided an explanation to understand the electronic structure, magnetism and reactivity of our catalysts. Core@shell (Mm@Nin) nanoparticles of 13-, 54- and 55-atoms with different elements concentrations matched the experimental results and assisted us with a better understanding of some of the microscopic phenomena involved with the reactivity of bimetallic nanoparticles.

A complex arrangement of electronic states within materials can manifest exotic quantum-mechanical effects. These systems are often referred to as quantum materials. Increased understanding of quantum materials has historically lead to the development of new technologies. It is therefore extremely important to develop and test precise methods for calculating the behaviour of electronic states within a material. For decades, the workhorse of electronic structure calculations has been density functional theory (DFT). DFT is often referred to as a first-principles method because it allows for the calculation of the distribution of electrons throughout a material with only specification of the lattice geometry and atomic components. From the results of a DFT calculation, it is possible to study the orbital character of electronic wavefunctions, topology of electronic band structure, and some aspects of superconductivity. This provides insight into many quantum properties of a system which may otherwise be difficult or impossible to ascertain from experiments. DFT is, however, sometimes limited by the approximations necessary for practical implementation. Further methods have been developed to systematically correct the limitations of DFT. In particular, the combination of DFT with dynamical mean-field theory (DFT+DMFT) is among the most widely accepted methods for correcting the inadequacy of DFT in handling strong electron-electron correlations. In this thesis, I use methods from DFT and DFT+DMFT to study the quantum properties of materials. / Thesis / Master of Science (MSc)

Heterodinuclear and homodinuclear metal complexes with a direct metal-metal interaction offer the potential for unique catalysis due to cooperativity effects that impact reaction mechanisms, reactivity, and selectivity. Quantum-chemical density functional theory (DFT) calculations can directly examine the origin of dinuclear reactivity and selectivity effects. Chapter 1 provides a short overview of heterodinuclear and homodinuclear catalysts that have been experimentally and computationally examined. Chapter 2 reports our study using DFT methods to understand the mechanism and reactivity of a heterodinuclear Co-Zr catalyst with phosphinoamide ligands that catalyzes a Kumada coupling between alkyl halides and alkyl Grignards. Chapter 3 reports DFT calculations that determine the mechanism for homodinuclear Ni-Ni promoted intramolecular vinylidene"“alkene cyclization.