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Showing 1 to 20 of 25 for “"Atomic orbitals"”.
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Toward high thermoelectric performance of solids: ab initio forces within the orthogonalized linear combination of atomic orbitals method
… groundwork for the calculation of interatomic forces in ab initio calculations using 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 …
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Introduction of a Fully Relativistic Capable Basis Set in the ab initio Orthogonalized Linear Combination of Atomic Orbitals Method
… scalar relativistic descriptions of the atomic orbital wave functions 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 …
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Electronic Structure in the Organic-based Magnet [Feᴵᴵ(TCNE)(NCMe)₂][FeᴵᴵᴵCl₄] using the Orthogonalized Linear Combination of Atomic Orbitals Method with Hubbard U
… using 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. …
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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 …
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Electronic structure and optical properties of layered ternary transition-metal carbides and nitrides
… orthogonalized linear combination of atomic orbitals (OLCAO) method. These layered ternary transition-metal carbides and nitrides are also commonly referred to as "MAX phases". Trends were observed for the calculated density of states (DOS) at Fermi-level, with respect to elemental …
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Efficient Automated Generation of Local Descriptors for Use in ab initio Electronic Structure Simulations
… is designed to automate the generation of local atomic environment descriptors for single element systems. The descriptors may be used for training neural networks to predict the set of electronic potential function coefficients, {Ai}, that are used within the DFT based orthogonalized linear …
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Electronic structure and transport in molecular and nanoscale electronics
… on Green's 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 …
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Enabling Electronic Structure Calculations of High Z Element Containing Materials Using Dirac Relativistic DFT Methods
… and four-component fully relativistic atomic orbital basis sets of Gaussian-type functions. A minimal norm least squares method was used to fit numerically represented, four-component Dirac spinors into a set of Gaussian basis functions possessing exponential coefficients expressed over …
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Application of ab initio calculations to collagen and brome mosaic virus
… The Orthogonalized Linear Combination of Atomic Orbitals (OLCAO) method is wellsuited for application to such large proteins. However, a new approach to reduce the computational cost and increase the computational feasibility is required and this extension to the method we call the …
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Advancing the treatment of relativistic theory within the OLCAO package and with application to solar photovoltaic technologies
… can be used to investigate the surface atomic and electronic structures of such materials (e.g., by observing core-level chemical shifts), theoretical support is vital for interpreting the measured data and for guiding the selection of future experiments. Unfortunately, perovskite solar …
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Application of Ab Initio Calculations and Molecular Dynamics to Collagen and Brome Mosaic Virus
… In this thesis, we have calculated ab initio atomic partial charges for proteins of collagen and the brome mosaic virus (BMV) capsid. These proteins contain from 1000-3000 atoms and efficient and accurate ab initio quantum modeling methods have only become more recently available for systems …
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Quantum Embedding Methods for the Accurate Ground and Excited Electronic Structure of Large Molecular Systems
… orbital localization, utilizing intrinsic atomic orbitals. The BE matching condition is restricted to well-localized orbitals, which allows BE to converged to at least 99\% of the correlation energy in basis sets up to cc-pVDZ. For the troublesome cases involving more diffuse and …
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Ab initio computational applications to complex biomolecular systems
… original length). The variation of total energy, atomic configuration, and the electronic structure during this process were analyzed in details. At the extension of ~1.3-fold, the ring opening reactions occurred in the backbones. The backbone nicks appeared at elongations of ~1.40-fold. The whole …
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The magnetic and electronic structures of several rare earth-transition metal intermetallic compounds
… by the orthogonalized linear combination of atomic orbitals (OLCAO) method. Calculations of magnetic moments, total energy, which is related to the preference of Fe occupying the 3g site, and total density of states are consistent with the results from SQUID measurements, neutron diffraction …
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Ab initio computational applications of electronic structure and spectroscopic Properties of bulk Crystalline materials
… ab initio orthogonalized linear combination of atomic orbitals (OLCAO) method. Based on available experimental data, the calculated electronic structure, dielectric functions and XANES spectra reproduce the experimental measurements very well. Electronic structures show that α-r-B12, γ-B28, …
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Understanding and Controlling the Optoelectronic Properties of Cs2AgBiBr6 Double Perovskite
… energy mismatch between the Bi and Sb s and p atomic orbitals, coupled with their non-linear mixing, results in the alloys adopting a smaller bandgap than the pure compounds. For the third area, I show that despite Sb alloying lowering the bandgap, there is a strong decrease in the power …
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Impurities in Antiferromagnetic Transition-metal Oxides – Symmetry and Optical Transitions
… between the electrons in the anisotropic d orbitals, which conventional band theory cannot describe adequately. The correlation problem is approached here by the well-accepted method of adding a Hubbard potential energy term to the ground state Hamiltonian, calculated within Density …
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In search for 3d/4f- and 4f-metal complexes with interesting magnetic and/or optical properties
… of the unpaired electrons in the inner 4f atomic orbitals. This has resulted in limited interest in the use of 4f-metal ions for the preparation of 3D molecule-based magnets. In contrast to this, for the case of SMMs, the fact that the magnetic anisotropy is a major requirement to see this …
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Modeling generation and characterization of attosecond pulses
… These pulses can serve as a probe to resolve atomic attosecond dynamics and image atomic orbitals and molecular motion. Due to high spatial and temporal coherence, high-order harmonic radiation can also be used to seed free electron lasers, which allow the generation of high-intensity X-ray …
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Exploration and Optimization of the One- and Many-particle Basis Sets in Modern Explicitly Correlated Electronic Structure
… or real-space methods, the linear combination of atomic orbitals (LCAO) approach using Gaussian atomic basis sets is still the most popular method for the simplicity of the underlying technology and the low computational cost. Gaussian basis sets require either basis set extrapolation or the use …
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