Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 232 for “"orbitals"”.
-
Fock's representation for molecular orbitals
V. Fock studied the hydrogen atom problem in momentum space by projecting the space onto a 4-dimensional hyper-sphere. He found that as a consequence of the symmetry of the problem in this space the eigen-functions are the R<sub>4</sub> spherical harmonics and that the eigenvalues are determined …
-
Linear scaling density functional theory with Gaussian orbitals and periodic boundary conditions
… density functional method with Gaussian orbitals for systems with periodic boundary conditions (PBC). When solving iterative self-consistent field (SCF) equations of density functional theory (DFT), the most computationally demanding tasks are Kohn-Sham (or Fock) matrix formation and the …
-
Development and Assessment of Pair Natural Orbitals Coupled Cluster Quadratic Response Properties
… techniques, such as local pair natural orbitals (LPNOs), these advancements allow us to match experimental results and probe the fundamental behavior of complex systems. However, while significant progress has been made for ground-state energetics, such as reaction pathways and binding …
-
Toward high thermoelectric performance of solids: ab initio forces within the orthogonalized linear combination of atomic orbitals method
… the Orthogonalized Linear Combination of Atomic Orbitals (OLCAO) method. The approach is based on the Hellmann-Feynman (HF) theorem and Pulay forces in the presence of an atomic orbital basis set. To accomplish this, we offered a thorough derivation of a HF theorem that holds for all quantum …
-
Introduction of a Fully Relativistic Capable Basis Set in the ab initio Orthogonalized Linear Combination of Atomic Orbitals Method
… from Grasp2K numerically represented atomic orbitals. In addition, adapted theory for the calculation of the relativistic kinetic energy contribution to Hamiltonian which bypasses directly solving the Dirac equation has been explicated. The orbital description improvements are tested against …
-
Ab Initio Treatment of Complex Systems Kohn-Sham Orbitals for Multi Reference Methods and the Base Pairing Properties of Xanthine
… der LHF-Ansatz zu einem vollständig gebundenen Orbitalspektrum, da Coulomb-Selbstwechselwirkungen im LHF-Ansatz exakt korrigiert werden. Durch die Korrektur der Coulomb-Selbstwechselwirkungen sind im LHF-Ansatz auch die Energien der besetzten Orbitale nicht wie in Standard-DFT-Methoden zu …
-
Electronic Structure in the Organic-based Magnet [Feᴵᴵ(TCNE)(NCMe)₂][FeᴵᴵᴵCl₄] using the Orthogonalized Linear Combination of Atomic Orbitals Method with Hubbard U
… the Orthogonalized Linear Combination of Atomic Orbitals (OCLAO) methods. The Local Spin Density Approximation (LSDA) method plus the Hubbard U parameter is used to account for on-site atomic Coulombic repulsion and exchange correlation interactions for the d orbitals of the FeII atoms. Applying …
-
Electronic structure and transport in molecular and nanoscale electronics
… function method with ab initio quasiatomic orbitals within Landauer formalism. To efficiently and accurately apply Green's function method, we develop a minimal basis-set of quasiatomic orbitals from plane-wave density functional theory (DFT) results. This minimal basis-set resembles …
-
A Computational Analysis of Supported and Unsupported Group 6 Transition Metal-Metal Bonds Based on the Natural Orbitals for Chemical Valence (NOCV) and the Extended Transition State (ETS) Techniques
… the extended transition state (ETS) and natural orbitals for chemical valence (NOCV) methods. The analysis of the unsupported triple (M2L6) and quadruple (M2L2L´2; M=Cr,Mo,W; L,L´=π-acceptor/σ-donor ligands) metal-metal bonds demonstrated that the M-M bond strength follows the trend Cr<<Mo<W, a …
-
Experimental and theoretical investigation of the electronic structures of ferrocene-peptide conjugates
… respectively. The identities of the finalstate orbitals corresponding to all near-edge features in the XAS spectra of all elements in the molecules are determined by comparison with published results for other systems, as well as density functional theory (DFT) spectral simulations. Experimental …
-
Implementation and reassessment of the Perdew-Zunger self-interaction correction
… previous applications of PZ-SIC restricted the orbitals to be real functions and did not take into account that orbitals are in general complex. The implications of the restriction to real orbitals were explored in detail in this thesis project and it was found that the effect on the total …
-
Electronic Structure of Three Center Two Electron Bonds in Boron Rich Materials: A Study of Molecules, Crystals, and Amorphous Solids using the ab initio Orthogonalized Linear Combination of Atomic Orbitals Method
… of electrons to populate all the molecular orbitals that would nominally be required for molecular cohesion. To overcome that electron deficiency, the icosahedral boron units tend to form interesting bonding structures with their neighbors in solids, and/or for molecular boron the icosahedra …
-
A study of some co-ordination compounds formed between nickel diammines and the nitrite ion
… of the hybridisation of (n - 1)d, ns and np orbitals to explain the two classes 'ionic' and 'covalent' into which co-ordination compounds of transition metals appeared to fall. These two classes in general have different numbers of unpaired spins, hence they will be distinguished by their …
-
Wannier Functions and Their Role in Improving Density Functional Approximations
… For bulk systems the delocalized nature of the orbitals results in a linear total energy at fractional charges, but the slope is incorrect due to delocalization error. Multiple methods have been proposed to fix this deficiency and produce the correct linearity condition such asthe Fermi-Löwdin …
-
Machine-Learned Representations of Basis Sets and Their Application in Quantum Computational Chemistry
… a Hermitian matrix encoding optimized molecular orbitals. The eigenvectors of this matrix define a transferable and efficient basis set, trained on orbitals obtained via CASSCF and Hamiltonian ℓ1 norm optimization. We evaluate our model on hydrogen chains and demonstrate that the predicted bases …
-
Approximate Spin Extended Hartree-Fock theory
… in which the Occupation Numbers of the Natural Orbitals of Charge are varied but the orbitals themselves are frozen. A number of techniques for obtaining appropriate Natural Orbitals of Charge are presented and these techniques are employed in semi-empirical and Ab-Initio studies. The molecules …
-
Calculations of small transition metal molecules relating to catalysis
… It was found that the transition metal 3d-orbitals do not participate significantly in the bonding of these molecules. Rather, the bonds involve mainly the 4s and 4sp hybrid orbitals. The diatomic hydride molecules were found to have a radical state with a highly reactive singly occupied …
-
Investigation of structural properties in biomolecular systems using synchrotron-based spectroscopies
… scale, the level of single bonds and molecular orbitals, is addressed in the last example where it was tried to elaborate an approach to map the topology of molecular orbitals based upon X-ray absorption properties. This approach was put to the practical test for the characteristic pi*peptide …
Page 1 of 12